Henry, Descartes And The Importance Of Laws Of Nature-2

Metaphysics and the Origins of Modern Science: Descartes and the Importance of Laws of Nature Author(s): John Henry Reviewed work(s): Source: Early Science and Medicine, Vol. 9, No. 2 (2004), pp. 73-114 Published by: BRILL Stable URL: http://www.jstor.org/stable/4130152 . Accessed: 30/01/2013 06:58 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp

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METAPHYSICS AND THE ORIGINS OF MODERN SCIENCE: DESCARTES AND THE IMPORTANCE OF LAWS OF NATURE* JOHN HENRY University of Edinburgh

Abstract This paper draws attention to the crucial importance of a new kind of precisely defined law of nature in the Scientific Revolution. All explanations in the mechanical philosophy depend upon the interactions of moving material particles; the laws of nature stipulate precisely how these interact; therefore, such explanations rely on the laws of nature. While this is obvious, the radically innovatory nature of these laws is not fully acknowledged in the historical literature. Indeed, a number of scholars have tried to locate the origins of such laws in the medieval period. In the first part of this paper these claims are critically examined, and found at best to reveal important aspects of the background to the later idea, which could be drawn upon for legitimating purposes by the mechanical philosophers. The second part of the paper argues that the modern concept of laws of nature originates in Ren6 Descartes's work. It is shown that Descartes took his concept of laws of nature from the mathematical tradition, but recognized that he could not export it to the domain of physico-mathematics, to play a causal role, unless he could show that these laws were underwritten by God. It is argued that this is why, at an early stage of his philosophical development, Descartes had to turn to metaphysics.

In a paper published in the USA in 1942, the emigre German Marxist historian, Edgar Zilsel, first drew attention to the fact that the concept of the law of nature, which had been only very occasionally explicit in theological discussion throughout the Middle Ages and the Renaissance, suddenly became so frequently invoked in seventeenth-century natural philosophy that, by the end of the * Earlier (barely recognizable) versions of this paper were read at the History Department, University of Durham (1999), and the History and Philosophy of Science Departments at the Universities of Melbourne and Leeds (2002). I am grateful to all those present who tried to help me make sense of the topic, especially Helmut Heit, Jonathan Hodge, Keith Hutchison, Martin Leckey, and Howard Sankey. I am also grateful to two anonymous referees who helped me to improve this paper. I must also apologise to them, however, for not being able to carry out all their suggestions. Would that I had the knowledge, and the skills as an historian, philosopher, and writer to have done so. ? Koninklijke Brill NV, Leiden, 2004 Also available online - www.brill.nl

Early Science and Medicine 9, 2

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century, it had become a commonplace in scientific discussion (and has remained so, ever since).' Indeed, since the end of the seventeenth century it seems true to say that a major aspect of the scientific enterprise has precisely been to discover those observed regularities in nature which are assumed to reflect an underlying causal necessity and which are then designated as laws of nature. The discovery and understanding of "Laws of Nature" is, as Zilsel noted, the basic task of science. It might even be said to be its defining characteristic: "Where there is no law," wrote Emile Meyerson, "there is no science."2 So, this presents us with an historical problem. Why was it that the concept of laws of nature came to be seen as an essential element of natural philosophy in the seventeenth century, while previously, for centuries past, this way of understanding natural phenomena had attracted little or no attention? Given the importance of the concept of laws of nature in modern science, it might be expected that the literature on this topic in the history of science would be extensive. Remarkably, this is not the case. In spite of a number of attempts to understand the historical development and importance of the concept of laws of nature, it remains true to say that "the full historical novelty, context, and extent of this general idea has not yet received its due."3 It is almost as though the idea of laws of nature is so prominent in Re1 Edgar Zilsel, "The Genesis of the Concept of Physical Law," Philosophical view 51 (1942), 245-79. Now reprinted in Diederick Raven, Wolfgang Krohn, and Robert S. Cohen (eds.), Edgar Zilsel: The Social Origins of Modern Science (Dordrecht, 2000), 96-122. Throughout this paper I use the phrase "law(s) of nature" rather than the more succinct "natural law(s)," to avoid any confusion with the legal and ethical notion of "natural law," i.e. moral laws which, generally speaking, are held to be either intuitively obvious to everyone, or capable of being arrived at by reasoning from obvious and undeniable premises. So far the historiography of these two concepts of laws in nature have been largely separate, but there may well be much to be learned on both sides by considering the two notions together. I have not attempted to enter this comparatively unbroken ground here, however. Our concern is entirely with laws of nature in the scientific sense. For a discussion which does bring the two concepts together see, for example, Thomas Ahnert, "De Sympathia et Antipathia Rerum: Natural Law, Religion and the Rejection of Mechanistic Science in the Works of Christian Thomasius," in T. J. Hochstrasser and P. Schr6der (eds.), Early Modern Natural Law Theories: Contexts and Strategies in the Early Enlightenment (Dordrecht, 2003), 257-77. 2 Emile Meyerson, Identity and Reality (London, 1930), 25. See p. 19 for sample quotations showing the importance of the notion of laws of nature to various scientists. 3 Eugene M. Klaaren, Religious Origins of Modern Science: Belief in Creation in Seventeenth-CenturyThought (Grand Rapids, 1977), 164.

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our modern understanding of the world that its presence in the historical record is taken for granted and scarcely examined.4 The aim of this paper is to draw attention to this lacuna, and to begin, perhaps, to fill it. Accordingly, the paper begins with a survey of the recent literature which has specifically dealt with the concept of laws of nature, in order to show, firstly, that writers on the topic have failed to provide a satisfactory historical understanding of its origins, and secondly, to indicate the fundamental importance of the concept for the Scientific Revolution. I pursue this latter point further in the second half of the paper, by arguing for the absolutely crucial importance of the laws of nature in Cartesian natural philosophy, and in the mechanical philosophy more generally. The Laws of Nature: A Survey of Recent Historiography There have been a number of attempts to sketch out a history of the concept of laws of nature, and although such accounts differ from one another, they all seem to point to one of three general conclusions. What I want to do here is to assess these differing approaches, and to see if we can decide between these rival claims about the origins and significance of the concept of laws of nature. Following Zilsel's lead, scholars who have tried to account for the rise of the concept of laws of nature have offered brief surveys of the use of the concept of laws of nature in pre-modern thought.5 4 This feeling is based upon my extensive reading of the secondary literature on early modern science. Indeed this paper arises out of my own frustration about the lack of extensive treatments of the topic which I noticed while writing a short text-book on the Scientific Revolution which incorporated a detailed literature survey: John Henry, The Scientific Revolution and the Origins of Modern Science (Basingstoke, 1997, revised 2002). I felt unable to refer students to a good guide to the topic, and consequently could not give the emphasis to it in my own discussion that I felt it deserved. It was at this point that I determined to write this paper. For confirmation of the lack of focus on laws of nature in the literature see H. Floris Cohen, The Scientific Revolution: A Historiographical Inquiry (Chicago, 1994), which, quite justifiably, offers no specific discussion of this topic (although the laws of nature are often mentioned in passing, e.g. 453-5). Cohen did regard Zilsel's recognition of the historical problem as his "most perceptive contribution to the history of science," 453. All the more reason, in my view, to consider it more fully. 5 See Zilsel, "Genesis of the Concept," 247-67. See also Joseph Needham, "Human Law and the Laws of Nature," in idem, The Grand Titration: Science and Society in East and West (London, 1969), 299-331 (first published in Journal of the History of Ideas 12, 1951) especially 299-311; idem, Science and Civilization in China, vol. 2

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A look at any one of these surveys is enough to convince us that the concept of laws of nature played at best a very minor role in natural philosophy beforethe seventeenth century, and it was a far cry from the kind of concept we see in Descartes, Newton and subsequent science. If we look at all of the surveys, however, something else becomes clear. The significance of pre-Cartesian instances where laws of nature seemed to be invoked is, perhaps inevitably, judged in accordance with each scholar's preconceived explanation of the origins of the concept. So, for example, Zilsel, who wants to explain the origin of laws of nature in terms of social and economic changes in the sixteenth and seventeenth centuries, is able to dismiss all pre-modern notions of laws of nature as irrelevant to our historical understanding. One of the worst cases of special pleading here is Zilsel's claim that Augustine's and Thomas Aquinas's discussions of God's eternal law as it is imposed on all creatures, not just humankind, can be dismissed on the grounds that they are "identical with the impenetrable providence of God" and are considerably distant from the modern concept of physical law.' Needham, who believed that Zilsel's explanation "must surely be in principle the right one," similarly emphasizes the evidence that suggests the newness of the idea of laws of nature in the early modern period.7 By contrast, Francis Oakley and John R. Milton, who both wish to explain the rise of the concept of laws of nature in terms of medieval nominalist philosophy, voluntarist theology and, pace Zilsel, other aspects of "the idea of divine providence," concentrate upon what they see as the richness of discussions about natural law and laws of nature in the Middle Ages. So, although Milton is willing to agree with Zilsel that the ancient references to laws of nature were so few in number that they could be disregarded, he refuses to agree with Zilsel's dismissal of the medieval references on the same grounds. Milton insists that the medieval references are sufficiently numerous that they cannot be "brushed aside," even though the number of medieval authors he cites is no greater than the number of ancient authors cited by Zilsel or Needham.8 (Cambridge, 1956), 518-83; Francis Oakley, "Christian Theology and the Newtonian Science: The Rise of the Concept of the Laws of Nature," Church History 30 (1961), 433-57, see 433-37; John R. Milton, "The Origin and Development of the Concept of the Laws of Nature," Archives Europ~ennes de Sociologie 22 (1981), 173-95, see 173-77. 6 Zilsel, "Genesis of the Concept," 256-7. 7 Needham, "Human Law," 309, see also Science and Civilisation, 2: 542. 8 Milton, "Origin and Development," 183.

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Milton dismisses many of the reported allusions to laws of nature by ancient thinkers on the grounds that they are often anachronistic translations, in which a post-Newtonian translator has read modern ideas into the classical text.' Nonetheless, it seems hard to dismiss the ancient examples provided by Needham or, to introduce another contributor to this debate, by Alistair Crombie. Admittedly laws of nature play a somewhat taken-for-granted role in Crombie's monumental and magisterial Styles of Scientific Thinking in theEuropean Tradition, but it is by no means possible to reject all the instances of early uses of laws of nature which he mentions. The belief that "laws"are immanent in the nature of things, so that knowledge of their natures leads inexorably to a knowledge of their relations with all other things, which Oakley sees as "typified by Stoic... views," is found by Crombie in Plato and the ancient Atomists.10 Furthermore, the shift from ideas of immanent law to the supposedly Semitic concept of imposed laws of nature, which Oakley locates in the Christian Middle Ages, is noticed by Crombie in the writings of Philo Judaeus. It was Philo, according to Crombie, who rejected earlier Greek ideas of "laws of nature arising entirely out of necessity in the nature of matter alone," which he found in Platonic, Aristotelian and Stoic thought, and conceived of a "system of principles introduced in the act of creation into the world as its immutable laws." Philo's ideas found their way into early Christian thought, as can be seen in the writings of Basil of Cappadocia in the fourth century AD, and in those of Augustine of Hippo in the sixth century.11 "Les lois de 9 Milton "Origin and Development," 174. See also, Sophie Roux, la nature au XVIIe siecle: le probl&me terminologique," Revue de synthise, 4e Series, 2-4 (2001), 531-76. 10 Oakley, "Christian Theology and the Newtonian Science," 435. Alistair Crombie, Styles of Scientific Thinking in the European Tradition: The History of Argument and Explanation especially in the Mathematical and Biomedical Sciences and Arts, 3 vols. (London, 1994), 1: 119-22. It has to be said, however, that a systematic examination of all the references to laws of nature in Crombie's index will prove that Milton has a point. In some cases an indexed page bears no explicit mention of laws of nature but is concerned with regular operations of nature or beliefs about the necessary connection of cause and effect. See, for example, 257-8, which is cited in the index under "nature, laws of' (3:2446). On the other hand, as far as A. N. Whitehead is concerned, the regular order of nature and belief in a necessary connection between cause and effect is tantamount to a belief in laws of nature. See A. N. Whitehead, Adventures of Ideas (Cambridge, 1933), 139. 11 Crombie, Styles of Scientific Thinking, 120, and 294-300. See also, idem, "Infinite Power and the Laws of Nature: A Medieval Speculation," in Science, Art and Nature in Medieval and Modern Thought (London, 1996), 67-87.

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In a recent revisitation of the history of laws of nature for the CambridgeHistory of Seventeenth-CenturyPhilosophy,John Milton illustrates the familiarity of the notion of laws of nature to seventeenthcentury audiences by quoting Francis Bacon: "Kings ruled by their laws as God did by the laws of nature, and ought as rarely to use their supreme prerogative as God doth his power of working miracles." Milton's point is that a remark like this would not have been made if Bacon thought that it was too obscure to be understood. But this is surely an argument of universal application."2 What are we to make of Plato's occasional use of the concept of law of nature? Would he have said, in passing as it were, that when a person is sick their blood extracts components of their food "contrary to the laws of nature," if he did not think his audience would understand what he meant?"3 Would Ulpian, the Roman jurist whose works later came to make up a significant proportion of the Justinian CorpusJuris Civilis, have opened the Digest with a reference to natural law as "That which all animals have been taught by Nature," if he had anticipated baffled responses from his fellow jurists?'4 "Curiously," wrote Needham, "it is in Ovid... that we find the clearest statements of the existence of laws in the non-human world." It would be especially curious, would it not, if Ovid used the notion of laws of nature in his poetry with no realistic expectation that his readers would have a clue as to what he was talking about?'5 We could say the same of all the pre-seventeenth-century references to laws of nature, from the Stoics to Georgius Agricola and from the Vulgate Bible to Richard Hooker, unearthed by Zilsel, Needham, Oakley, and Milton. In the light of these references, scattered though they may be over a period of two millennia, it seems hard to resist the conclusion that the educated in all ages (Zilsel and Needham even find "Laws of Nature," in Daniel Garber and M. Ayers (eds.), The "12John Milton, CambridgeHistory of Seventeenth-CenturyPhilosophy (Cambridge, 1998), 680-701, 684. See also Milton, "Origin and Development," 182-3; and, for the original source, Francis Bacon, Advancement of Learning, Book II, in J. Spedding, R. L. Ellis and D. D. Heath (eds.), The Worksof Francis Bacon, 7 vols. (London, 1857-1861), 3: 429. 13 Plato, Timaeus, 83e. Quoted in Zilsel, "Genesis of the Concept," 250; Needham, "Human Law," 302; Milton's caution against being misled by anachronistic translations ("Origin and Development," 174) is evidently not relevant here, as this seems to be a very clear case where Plato really does use the word law (nomos). "Human 14 The Digest ofJustinian, I, 1, 3. Quoted in, and cited from, Needham, Law," 305; Zilsel, "Genesis of the Concept," 255. 15 Needham, "Human Law," 303. Cited also by Zilsel, "Genesis of the Concept," 251.

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references to laws of nature among the Babylonians, which take us back nearly four millennia'6) found it easy to understand the general notion that physical phenomena took place in accordance with, or as though they were governed by, "laws" of nature. Perhaps, then, Emile Meyerson was being less fanciful than he seemed when he attributed the concept of laws of nature even to "primitive man.""7 The unmistakable conclusion from all these accounts is that the notion of laws of nature, in some form or other, can be found very early in Western (if not world) civilization and could be said to be an idea which was always readily understood by the educated. Needham largely acknowledged the agelessness of the concept by referring to the idea of laws of nature as "a theological commonplace in European civilization." There is no need, therefore, for historians to explain the rise of the concept, whether gradual or sudden. It seems reasonable to suppose, from its longue duree, that it was a metaphor which could occur almost naturally to the human mind. Perhaps an attempt to discover the origins of the metaphor of laws of nature is as futile as trying to discover the origins of the suggestion that a great warrior was as fierce as a lion. We should not let this be the last word on the subject, however. It is perfectly clear that all these early references to laws of nature are merely references to the regularity of nature. According to this usage it is one law of nature that the sun rises in the morning, and another that bees make honey. This is not what modern scientists mean by laws of nature. Our concern here is with the concept of a law of nature as a specific and precise statement which codifies observed regularities in nature but which is also assumed to denote an underlying causal connection, and therefore can be said to carry explanatory force.'" A law of nature in this sense is not simply a statement of an observed regularity but a formalized state16

Needham, "Human Laws," 301, and Science and Civilisation, 2: 533. " Meyerson, Identity and Reality, 20. 1s This is, of course, only a working definition, which I hope serves our purposes here. Needless to say, the nature or status of laws of nature continue to attract the attention of philosophers of science, and there are a number of rival definitions which are incompatible with one another. For a convenient and excellent summary of the philosophical state of play see the editor's introduction, "Laws of Nature-Laws of Science," in Friedel Weinert (ed.), Laws of Nature: Essays on the Philosophical, Scientific and Historical Dimensions (Berlin, 1995), 3-64. I have included "causal connection" in my working definition for reasons that will become apparent later. In the meantime, in my defence, I should perhaps remind the reader that we are concerned here with ideas about the laws of nature before David Hume.

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ment of a fundamental regularity which can be shown to explain a wide range of physical phenomena. The clearest examples of laws of nature in this sense are found, of course, in Descartes's Principia philosophiae of 1644, and Newton's Principia mathematica of 1687. According to Zilsel this conception of laws of nature was entirely new in the seventeenth century. He effectively disregarded the earlier instances of laws of nature which he had uncovered, of laws of therefore, and asked why this new conceptualization nature suddenly became so important in seventeenth-century natural philosophy. For Needham, likewise, the historical problem which needed to be addressed was not how the concept of physical laws originated, but why it suddenly became so radically different, and so crucially important in "the sixteenth and seventeenth centuries."'9 Similarly, although Crombie had a marked tendency to take the notion of laws of nature for granted as an essential ingredient in all "styles of scientific thinking," from ancient times onward, he nevertheless discerned a major transformation of the idea in the seventeenth century."0 More recently, Friedrich Steinle in a thorough and judicious examination of the concept of laws of nature has pointed out that in the seventeenth century there was "a process of fundamental change in what one is willing to accept as causes of phenomena," culminating in "an intimate connexion of causes and laws," so that "causal explanations cannot be constructed without laws."2' There is no consensus on this matter, however. There is a powerful group of historical studies devoted to the claim that the transformation of the laws of nature from loose metaphors of nature's regularity to more precise codifications of underlying causal connections took place in the medieval period. For Francis Oakley, John R. Milton and Amos Funkenstein, the transformation of laws of nature took place in the thirteenth century and was ready to be taken up by Descartes and others in the seventeenth century when they began to develop the so-called "new" philosophies. For all three of these historians, the important thinkers were a group of scholastic theologians, chiefly in the thirteenth century, concerned with the nature of divine providence. Jane E. Ruby, on the other 19 Needham, "Human Law," 309. 20 Crombie, Styles of Scientific Thinking, 57-8. 21 Friedrich Steinle, "The Amalgamation of Nature in the of a Concept-Laws New Sciences," in Weinert (ed.), Laws of Nature, 316-68, see 317, 337.

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hand, taking her lead from earlier work by Alistair Crombie,22 has made a major claim for the origins of the "modern" concept of laws of nature in a completely different group of medieval thinkers, from the thirteenth through the fifteenth century. Ruby is convinced of this by a usage of 'laws' in Roger Bacon's optics, and in the astronomy and mathematics of Regiomontanus, and other medieval mathematicians, which is "indistinguishable from ours," and which shows "no vestige of the idea of divine legislation."23 These three claims about the source of the transformation of the idea of laws of nature-in Cartesianism, in medieval provithe major hisdentialism, or in medieval mathematics-represent to this issue. What we must do toriographical positions relating is examine each of these in turn to see now, therefore, which, if as the most convincing. any, emerges Zilsel's solution to the historical problem he noticed evidently derived from his socialist political orientation and his socialist view of history.24 Consequently, he saw the rise in importance of the concept of laws of nature as a concomitant of "the decline of feudalism, the beginnings of capitalism, and the appearance of royal absolutism."25 According to Zilsel, the idea of God as a supreme lawmaker imposing his laws even upon inanimate nature could not have occurred to medieval thinkers, living under the kind of localized political system which was characteristic of feudal Europe: How could medieval theologians speak of the legislature of God, when the power of the prince was very limited? The idea, however, had not originated in feudalism. It had been conceived under entirely different sociological conditions. Its authors were Jews who had outgrown their past of Bedouin clan-organization... and its sociological pattern was the despotism of ancient oriental states. The idea could be preserved in a rudimentary form through two thousand years, even through a period in which it did not fit the sociological conditions, till it awoke to new life in early capitalistic absolutism.26

There were two aspects to Zilsel's explanation of the early modern 22 Alistair Crombie, "The Significance of Medieval Discussions of Scientific Method for the Scientific Revolution," in Marshall Clagget (ed.), Critical Problems in the History of Science (Madison, 1959), 79-101. 23 Jane E. Ruby, "The Origins of Scientific 'Law'," Journal of the History of Ideas 47 (1986), 341-59, 343, now reprinted in Weinert (ed.), Laws of Nature, 289-315. 24 See the Introduction by Diederick Raven and Wolfgang Krohn, in Raven, Krohn and Cohen (eds.), Edgar Zilsel, xix-lix, for an account of Zilsel's philosophy of history and its relationship to his political views. 25 So says Oakley, "Christian Theology and the Newtonian Science," 434, but it is a fair comment. See Zilsel, "Genesis of the Concept ," 276-79, and Needham, Science and Civilisation, 2: 543. 26 Zilsel, "Genesis of the Concept," 279.

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re-awakening of this idea. On the one hand, artisans and craftsmen, stimulated by economic competition, began to innovate and improve upon their normal craft techniques. "In all civilizations," Zilsel declaimed, "experimentation originates in handicraft." In the period of nascent capitalism experimenting artisans began to look for quantitative rules of operation. The roots of these mechanical rules, therefore, must be searched for in the sociological and technological conditions of handicraft in the early modern era. They rose to science in Galileo.27

On the other hand, the development of the political theory and practice of absolutism gave rise once again to the dormant idea of God as the supreme legislator. It is not a mere chance that the Cartesian idea of God, the legislator of the universe, developed forty years after [Jean] Bodin's theory of sovereignty. Perhaps it is not even a coincidence that both thinkers were French: France was the native country of centralized absolutism. At any rate the doctrine of universal natural laws of divine origin is possible only in a state with rational statute law and fully developed central sovereignty.28

It is difficult to find these claims historically convincing. Zilsel provides an example of the quantitative rules of experimenting artisans by referring to Niccolo Tartaglia's recognition of the relationship between elevation and range of cannons. But A. Rupert Hall undertook a detailed history of the development of ballistics in the seventeenth century and was able convincingly to refute Zilsel's claims about the role of artillery men in working out this relationship.29 Zilsel's more general claim that experimentation originated in handicraft is also highly contentious.30

This is not the

place to enter into a detailed account of the origins of the experimental method, but suffice it to say that the general consensus of historians of science is that the experimental method owes its

emergence to developments among mathematical practitioners, to natural philosophers paying greater attention to the natural magic tradition and to a rejection of ancient authority stimulated not just by observations of new fauna and flora made upon Renaissance voyages of discovery, and not just by new astronomical observaIbid., 276, see also 263-64. Ibid., 278-79. Ibid., 264. Zilsel cites Niccolo Tartaglia, Quesiti et inventioni diverse (1554), 1:1. A. R. Hall, Ballistics in the Seventeenth Century (Cambridge, 1952). 30 Zilsel deals with this issue in another article, "The Origins of William Gilbert's Experimental Method," Journal of the History of Ideas 2 (1941), 1-32. I have attempted a detailed refutation of this in my "Animism and Empiricism: Copernican Physics and the Origins of William Gilbert's Experimental Method," Journal of the History of Ideas 62 (2001), 99-119. 27 28 29

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tions, but also by the Renaissance discovery of numerous ancient philosophical texts providing unexpected alternatives to the dominant Aristotelian philosophy.3' Although some of these developments might look as though they could be made to fit in with the economic focus of socialist accounts, the historical details do not easily support that interpretation. Consider the example of the role of mathematical practitioners by way of example. While some historians have tried to suggest that the major stimulus towards empirical science among mathematicians was connected with navigation, surveying, and other obviously pragmatic and ultimately economic concerns, others have pointed to disputes over the best means of attaining certainty, so that mathematics came to be seen as a model of good practice in science, and the use of instruments, long used in mathematics, came to be accepted in natural philosophy and led to new ways of understanding the world.32 Besides, as Milton has pointed out, the first specific laws of nature, as seen in Descartes's Principia philosophiae, patently do not derive from the kind of low-level generalization that one would expect to be derived from craft rules of thumb." Moreover, it would be hard to see why or how craft rules could be culturally elevated in such a way that they came to be seen as laws imposed upon nature by God. If the work of Oakley and Milton shows anything (as we shall see shortly), it shows that when laws of nature emerged in the field of scientific enquiry, they were very quickly assimilated with earlier pre-existing theological doctrines about God's relationship to the world and its creatures. As to the putative links with absolutism, what can we say? It is possible that broad changes in political organization affect people's consciousness in such a way that they begin to think of God and references to further readings 31 For a summary of these developments see Henry, The Scientific Revolution, 14-60. "The Mechanics Philosophy and the Me32 See, for example, J. A. Bennett, chanical Philosophy," History of Science 24 (1986), 1-28; idem, "The Challenge of Practical Mathematics," in S. Pumfrey, P. Rossi and M. Slawinski (eds.), Science, Culture and Popular Belief in Renaissance Europe (Manchester, 1991), 176-90; Peter Dear, Discipline and Experience: The Mathematical Way in the Scientific Revolution (Chicago, 1995); Nicholas Jardine, "The Status of Astronomy," in idem, The Birth of History and Philosophy of Science: Kepler's A Defence of Tycho against Ursus with Essays on its Provenance and Significance (Cambridge, 1984), 225-57; James M. Lattis, Between Copernicus and Galileo: Christoph Clavius and the Collapse of Ptolemaic Cosmology (Chicago, 1994); and Robert S. Westman, "The Astronomer's Role in the Sixteenth Century: A Preliminary Survey," History of Science 18 (1980), 105-47. 13 Milton, "Origin and Development," 179.

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and his relationship to the world in a new way, but it is very difficult for the historian to pin this down. The argument has to be made impressionistically, and as such it differs markedly from the kind of argumentation and accompanying evidence upon which historians usually like to depend. If, then, it is safer to reject the claim, perhaps we need simply to point, as Oakley and Milton both do, to the existence of absolute monarchies in other parts of the world, and at other periods, where the concept of laws of nature never developed.34 Alternatively, we might point out the absurdity of Zilsel's suggestion that medieval theologians could not have conceived of the legislature of God when the power of their princes was so limited. In fact, as Oakley and Milton have no difficulty in showing, theologians were discussing the absolute power of God with great philosophical sophistication from at least the eleventh century onwards. Milton suggests that, if anything, the direction of influence was from theology to political theory, rather than the other way around.35 It could still be the case, however, that such theological ideas did not impinge upon natural philosophy until after they had begun to affect political thought and practice. Again, this is an impressionistic claim that cannot easily be refuted. But it cannot easily be proved either. And one thing is abundantly clear, in the seventeenth-century discussions of the laws of nature, the context is essentially theological, not political, and Oakley is certainly correct to see these discussions as continuous with medieval voluntarist theology.36 34 Oakley, "Christian Theology and the Newtonian Science," 434-5, Milton, "Origin and Development," 180. Indeed, it is a major part of Needham's intention in his study of the concept of laws of nature to explain why the concept never emerged in Chinese thought when, according to Zilsel's philosophy of history, it should have. See Needham, "Human Law" and Needham, Science and Civilisation, passim. 35 Milton, "Origin and Development," 180. See also Oakley, "Christian Theology and the Newtonian Science," 438-449, and Oakley, Omnipotence, Covenant and Order: An Excursion in the History of Ideas from Abelard to Leibniz (Ithaca, 1984). to this is the dispute between Leibniz and the Eng36 The possible exception lish Newtonians, as manifested in his epistolary exchange with Samuel Clarke. The political background to this dispute is emphasized in Steven Shapin, "Of Gods and Kings: Natural Philosophy and Politics in the Leibniz-Clarke Disputes," Isis 72 (1981), 187-215; and in Gideon Freudenthal, Atom and Individual in Newton's Natural Philosophy (Dordrecht, 1985). My own view, for what it is worth, is that both are right to point to a political dimension in this particular dispute. With regard to Shapin's paper, however, it is fair to say that thanks to the longstanding nature of the theological debate in which Leibniz and Clarke were engaged, the general themes of their dispute over the nature of God's power were bound to occur no matter what the political situation. No doubt the protagonists

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We can now turn our attention ham simply takes Zilsel's solution his energies in trying to account cal fact that absolutist China did

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to Oakley's solution since Needfor granted, and spends most of for the (consequently) paradoxinot develop a concept of laws of

nature.37

Oakley perceives a clear continuity between medieval theology and seventeenth-century natural philosophy, and insists that the theology somehow accounts for the rise to prominence of laws of nature in natural philosophy. What Oakley does in response to Zilsel's paper is to provide a history of changing ideas of Providentialism. Whereas Zilsel rejected the relevance of Augustine and Aquinas to the development of the concept of laws of nature on the grounds that they were really concerned with ideas of God's providence, Oakley insists that it is in these very theological ideas that we find the solution to our problem. "The real problem is this," Oakley wrote, "Why, after so many centuries of almost total noticed the political echoes of what they were saying, they may even have believed that their politics reflected their theology, but I very much doubt that they would have changed their theologically inspired, and highly traditional arguments to fit in with their politics. In other words, Shapin presents the dispute as a case study which illustrates his principle that any natural philosophy can be made to serve any political stance. For a statement of this principle see S. Shapin, "History of Science and Its Sociological Reconstructions," Histoy of Science 20 (1982), 157-211, 191, 194. This cannot be used to undermine the claim of Oakley and others that the theological tradition, continuous from the thirteenth century, predominates in the dispute. Freudenthal, on the other hand, offers a much more precise argument in which Newtonian views on absolute space and the behaviour of atoms reflect the bourgeois socio-political theory of the individual, while Leibniz's philosophy is much more in keeping with the non-bourgeois political tradition of which he was a part. Notwithstanding the vigorous criticisms of Keith Hutchison, "Individual, Causal Location, and the Eclipse of Scholastic Philosophy," Social Studies of Science 21 (1991), 321-50, this remains an enthralling and powerfully argued thesis. Even if true, however, it remains a lone example which does little to undermine Oakley's general claim that the usual context of discussions of laws of nature is theological. For a more philosophical account of the main issues in the Leibniz-Clarke exchange see Ezio Vailati, Leibniz and Clarke: A Study of Their Correspondence(Oxford, 1997); for the text see H. G. Alexander (ed.), The LeibnizClarke Correspondence(Manchester, 1956). For an explanation of why the context is theological see later, and Amos Funkenstein, Theology and the Scientific Imagination: From the Middle Ages to the Seventeenth Century (Princeton, 1986). 3 Needham, "Human Law," 311-30; Science and Civilisation, 2: 543-83. On the face of it, it looks as though Needham could equally well have used the Chinese case to refute Zilsel's claims about the link between absolutism and laws of nature. Presumably he didn't because he shared Zilsel's political view of the world and believed that absolutism ought to be linked to the rise of the science which they both saw as part of the capitalist enterprise; so China had to be anomalous. On Needham's sympathetic admiration for Zilsel see his "Foreword" in Raven, Krohn, and Cohen (eds.), Edgar Zilsel, xi-xiv.

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submersion in Greek ideas of immanent law, did the Semitic concept of imposed laws of nature burst into prominence in seventeenth century scientific thought?"38 Oakley sees the concept of immanent laws of nature as deriving from Stoic philosophy, in which the world is seen as "impregnated with reason," and natural laws are "universally valid and inherent in the very structure of things." In the Semitic concept of imposed laws of nature, however, all is ultimately dependent upon the will of God, and "there can be no question of these laws being intrinsic to the nature of things." In the Christian Middle Ages, Oakley claims, the two views were effectively united in a perhaps uneasy compromise position. He provides the following illustration: This somewhat uneasy compromise is evident in Aquinas. His God is, admittedly, a Christian God, omnipotent and transcendent, but his eternal law, which orders to their appointed ends all created things, irrational as well as rational, is undoubtedly immanent in the universe.3"

Oakley wants to suggest that the prominence of laws of nature in natural philosophy in the seventeenth century is the end result of a gradual shift in theological sensibility from this "quasi-immanent view of natural law" to a stricter adherence to the view of laws as imposed by an omnipotent God. Oakley's story involves the rise to prominence of voluntarist theology, so that it comes to overshadow the necessitarian theology which is more easily linked to notions of immanent law.40 There can be no doubt that Oakley succeeds in general terms in revealing the theological background to the speculations of the leading, religiously minded, mechanical philosophers, like Descartes, Boyle and Newton. It is less clear, however, that he succeeds 38 Oakley, "Christian Theology and the Newtonian Science," 437. 9 Oakley, "Christian Theology and the Newtonian Science," 436. See also 441-

2. Oakley cites Aquinas's Summa Theologica, Ia 2ae, qu. 94, art. 2 Resp. Oakley's assessment of medieval theology at this point is evidently drawn from A. N. Whitehead's Adventures of Ideas (New York, 1937), 142-47. 40 Oakley effectively expanded this same argument in his Omnipotence, Covenant and Order. Oakley's work, along with that of others, has recently been attacked for claiming a link between voluntarist theology and the development and character of modern science. See Peter Harrison, "Voluntarism and Early Modern Science," History of Science 40 (2002), 63-89. This is not the place to pursue this, but suffice it to say that I support Oakley's views in this regard, and hope to address a refutation to Harrison in a forthcoming paper. In the meantime for another important account of the role of voluntarist and necessitarian theologies in early modern science see Margaret J. Osler, Divine Will and the Mechanical Philosophy: Gassendi and Descartes on Necessity and Contingency in the Created World (Cambridge, 1994).

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in solving the historical problem pointed out by Zilsel. After all, as Oakley himself insists, "the idea of laws of nature imposed by God upon the world was undoubtedly common coinage in the sixteenth and seventeenth centuries, even before Descartes, Boyle and Newton made it a commonplace in scientific thinking." Oakley goes on to say that it was so widespread "precisely because it was the expression of a tradition in natural theology which dated back well beyond the late thirteenth century."41 What Oakley fails to do, therefore, is explain why Descartes, Boyle and Newton were among the first to make laws of nature a commonplace of "scientific" thinking. Why was it not taken up by natural philosophers before this, if it was an obvious concomitant of a natural theology which had been available since the late thirteenth century? It is one thing to claim, as Oakley does, that This remarkable coincidence between the views of fourteenth-century theologians and seventeenth-century scientists can only serve to confirm what we have already suggested-that they were linked by an enduring theological tradition.

It is quite another to explain why these scientists-or natural philosophers, as we should more properly say-quite suddenly saw the need to replay these old theological arguments in their natural philosophies.42 Nowhere in Oakley's account do we find any kind of historical motor driving the philosophical theology of John Duns Scotus and William of Ockham steadily towards seventeenthcentury natural philosophy. In fact, it is quite clear from Oakley's own meticulously detailed account that although the disputes over the nature of God's providence have been a major element of Western theological debate since at least the eleventh century, the notion of laws of nature does not much figure in these debates until after the appearance of the laws of nature in the scientific literature of the seventeenth century. It is certainly possible to imagine, therefore, that the disputes over the nature of Providence might have continued into the modern period without the new focus upon laws of nature, if the laws of nature had not come to prominence in the way that they did at that time. Conversely, these theological debates about the Oakley, "Christian Theology and the Newtonian Science," 446. 42Ibid., 445. This is particularly remarkable given the separation between theology and natural philosophy, on which see Edward Grant, The Foundations of Modern Science in the Middle Ages: Their Religious, Institutional, and Intellectual Contexts (Cambridge, 1996). 41

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nature of Providence do not appear in the writings of medieval natural philosophers, and so their appearance in the writings of thinkers like Descartes, Boyle, Spinoza, Newton and Leibniz suggest that something else has happened, to bring about changed perceptions of what pertains to natural philosophy. Oakley offers no real evidence that there is an historical continuity of this debate within natural philosophy. It seems to me that, in fact, the debate does not appear in natural philosophy until the appearance of the laws of nature as major elements in physical explanations in the writings of the first mechanical philosophers. It can hardly be denied that the theological discussions of the nature of God's providence were waiting to be exploited by natural philosophers, as soon as they recognised the need to have recourse to laws of nature. But this is a far cry from establishing that the theological debates, current since at least the thirteenth century, suddenly caused the new emphasis upon laws of nature in the seventeenth. Even with all its illuminating richness, therefore, Oakley's thesis seems to leave serious doubts as to why the laws of nature became so important when they did. A similar point can be made against the related claims of Alistair Crombie and Amos Funkenstein. Although Crombie categorically states that "The theological concept of ordained law became transformed into the scientific concept of natural laws," he does not explain how this happened. After describing the importance of the medieval distinction between God's absolute and ordained powers and its role in voluntarist theology, Crombie simply states that these ideas were "to have a long reach," and immediately switches to the early modern period, showing how these ideas appeared in the work of Francisco Suarez, Rene Descartes, Robert Boyle, and Isaac Newton.43 Similarly, Funkenstein, in what is the most detailed account of these matters, leaves the reader in no doubt about the intellectual continuity between the ideas of Scotus, Ockham, and other medieval voluntarist theologians, and Descartes, Boyle, Newton and Leibniz, but he says nothing about the actual historical continuity. The juxtaposition of the medieval and the seventeenthcentury arguments is evidently expected to speak for itself. Funkenstein talks of the role of scholastic thought in establishing some of the conditions necessary for the emergence of early modern 4 Crombie, Styles of Scientific Thinking, 400-08, quotation at 407; also in idem, "Infinite Power and the Laws of Nature," quotation at 86.

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science, but he only provides an impressionistic

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account of that

role.44

We can reject the conclusion of Milton's re-assessment of the origins of the concept of laws of nature on the same grounds. Like Oakley, Milton sees "the beginnings of the change in thought which led men to think of the physical world as being governed by laws" in the fourteenth century when there was a synthesis of nominalist philosophy and voluntarist theology.45 Milton is surely correct to say that this synthesis "provided a context within which the idea of a law of nature was both comprehensible and natural," but this in itself is not sufficient to explain the sudden importance of the laws of nature in seventeenth-century natural philosophy.46 The question remains: why did the early mechanical philosophers suddenly begin to exploit that theological context? Milton himself has recognized the incompleteness of his original thesis in a more recent survey of the history of laws of nature. Here he writes that "The idea that one of the main aims-perhaps the main aim-of a natural philosopher should be the discovery of the laws governing the natural world emerged clearly for the first time during the seventeenth century." Although he still takes the line that the medieval background is essential for a proper understanding of the way in which the concept of the laws of nature developed and became accepted, Milton nevertheless insists that the concept first appeared "as centrally important to scientific thinking in the seventeenth century."47 It would seem, therefore, that Milton now accepts that Zilsel had noticed a genuine historical problem, as to why the laws of nature became so important in natural philosophy when they did, and that this problem is not solved simply by looking back to the medieval background. Besides, Milton's latest excursion into the history of the concept of laws of nature explicitly undermines Oakley's and his own earlier thesis. While Milton previously accepted that the most important of the crucial elements in the development of the idea of laws of nature was "a belief in the radical contingency of the world, and hence of the laws of nature also," he now freely acknowledges that, in the seventeenth century, laws of nature could be, and were, conceived as being logically necessary.48 Among English thinkers 44 45 46

Funkenstein, Theology, 117-201, quotation at 152. Milton, "Origin and Development," 184, and 190.

Ibid., 191.

Milton, "Laws of Nature," 680-81. Milton, "Origin and Development," 194, Milton, "Laws of Nature," 693-99.

47 John 48

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the contingency of the laws of nature, as Milton rightly says, acquired the status of an orthodoxy, but Spinoza developed an extreme necessitarian conception of the laws of nature, in which the laws were so absolutely necessary that even God's omnipotence could not change or suspend them.49 Although Leibniz took a less extreme position, he is more correctly seen as a necessitarian than a voluntarist in his theological position. Leibniz's God was morally obliged to create the best of all possible worlds, and so the laws of nature which Leibniz believed God had established could not have been freely chosen, as an extreme voluntarist might have wished to claim.50 Indeed, even Descartes fails to conform to the standard Ockhamist tradition of voluntarist theology which Oakley sees as so important in the origins of the notion of laws of nature. Although Descartes believed that God was completely free to establish whatever laws he wished, having chosen, God's immutability (a foundational premise of Descartes's natural philosophy) ensured that He could not change them. Accordingly, Descartes was able to claim that the laws could be established a priori, in a way that entirely contingently maintained laws could not be.5" In view of all this it seems hard to accept the implication of Oakley that the laws of nature, as they appeared in the seventeenth-century mechanical philosophy, were merely the latest manifestation of an idea that had been entirely current since the thirteenth century in the tradition of voluntarist theology. I believe the work of Francis Oakley, John Milton, Alistair Crombie and Amos Funkenstein points to extremely important aspects of the background to the historical problem of the radical transformation of the concept of laws of nature, and play an important part in our understanding of the historical development of that conRi49 Milton, "Laws of Nature," 694. On Spinoza's theology see, for example, chard Mason, The God of Spinoza: A Philosophical Study (Cambridge, 1997). 5o Milton, "Laws of Nature," 693. On Leibniz see A. O. Lovejoy, The Great Chain of Being: A Study of the History of an Idea (Cambridge, Mass., 1936); and Oakley, Omnipotence, Covenant and Order, Funkenstein, Theology, 195-201; Jacques Jalabert, Le Dieu de Leibniz (Paris, 1960); Donald Rutherford, Leibniz and the Rational Order of Nature (Cambridge, 1995), 7-21. 51 Milton, "Laws of Nature," 694. On Descartes, see Funkenstein, Theology, 17992; and Margaret J. Osler, Divine Will and the Mechanical Philosophy. For the majority of English natural philosophers, the radical contingency of laws of nature went hand-in-hand with their empiricism. See, for example, John Henry, "Occult Qualities and the Experimental Philosophy: Active Principles in pre-Newtonian Matter Theory," History of Science 24 (1986), 335-81; idem, "Henry More versus Robert Boyle: The Spirit of Nature and the nature of Providence," in Sarah Hutton (ed.), Henry More (1614-1687): TercentenaryStudies (Dordrecht, 1990), 55-75.

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cept. Certainly, there can be no doubt of the relevance of providentialist disputes, and theological voluntarism in the efforts of Descartes, Boyle, Newton and Leibniz to justify their use of laws of nature. We only have to look at Principle 36 in Part II of Descartes's Principia philosophiae (1644) which precedes his introduction of the laws of nature, Boyle's FreeEnquiry into the VulgarlyReceived Notion of Nature (1686), and the Leibniz-Clarke correspondence of 1715-1716, to see this.52 But all this is best seen as the exploitation of a ready made theological tradition in support of their innovations, rather than as an explanation for those innovations. This brings us to the alternative medieval source of laws of nature, as proposed by Jane E. Ruby. Taking her lead from earlier work by Alistair Crombie, Ruby makes a major claim for the origins of the "modern" concept of laws of nature in the medieval period."3 Ignoring the undeniable fact that for Descartes, Boyle and Newton, to mention no others, laws of nature were inseparably connected with notions of God's providence, Ruby says that although "the explanation of scientific 'law' as arising from the idea of divine legislation is highly plausible it is for the most part mistaken." Ruby is convinced of this by a usage of "laws" in Roger Bacon's optics, and in the astronomy and mathematics of Regiomontanus, which is "indistinguishable from ours," and which shows "no vestige of the idea of divine legislation."54 The assumption that Bacon's use of laws in explicating his geometrical optics "was derived from the idea of divine legislation is quite unfounded," she insists. Similarly, law was used in fifteenth-century mathematics in "a recognizably modern sense," but "again, the idea of divine legislation played no part" in the origins of this usage.55 Ruby sees the origin of Roger Bacon's use of notions like the law of multiplication, or the law of refraction, in concepts of rules used 52 See, for example, Klaaren, Religious Origins of Modern Science; Oakley, Omnipotence, Covenant and Order, Funkenstein, Theology;John Henry, "Henry More versus Robert Boyle"; H. G. Alexander, The Leibniz-Clarke Correspondence; Ezio Vailati, Leibniz and Clarke;John Henry, "'Pray do not ascribe that notion to me': God and Newton's Gravity," in James E. Force and Richard H. Popkin (eds.), The Books of Nature and Scripture: Recent Essays on Natural Philosophy, Theology and Biblical Criticism in the Netherlands of Spinoza's Time and the British Isles of Newton's Time (Dordrecht, 1994), 123-47. 5 Chiefly, Alistair Crombie, Robert Grossetesteand the Origins of Experimental Science, 1100-1700 (Oxford: Clarendon Press, 1953). 54 Ruby, "Origins," 342, 343. 55 Ruby, "Origins," 342-3.

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in geometry and logic. The principle of contradiction was seen as so certain a rule, Ruby suggests, that by 1250 it was being referred to as the lex contradictionis. It seems reasonable to suppose, as she says, that Bacon used the term law in his geometrical optics to give similar emphasis to some of his optical principles. Ruby pursues the history of such optical laws to the seventeenth century, insisting that "Descartes might contend that even mathematical verities are the work of God; but the lex of optics reached modern times before him, independent of the idea of divine legislation."56 Similarly, she finds the notion of laws of nature evolving in the astronomical tradition from Regiomontanus, in whose writings the word means little more than regularities in nature, to Copernicus, A similar line is taken who is said to use the concept "as we do.""57 in his by Nicholas Jardine study of the background to Kepler, when he declares that the notion of leges motuum was in common use among astronomers throughout the sixteenth century.58 We have to be careful here, however. There seem to be two different usages of the term "law"in the mathematical traditions. On the one hand, the term law is used in the familiar loose way, to refer simply to the regularity of nature. When Copernicus talks of the "fixed laws of motion of the planets in the firmament," he is

hardly doing more than extending the commonplace notion that the sun will rise tomorrow by the law of nature. But there are some cases where law seems to refer to something more specific. Ruby

cites Bacon's often repeated talk of "law(s) of reflection," "law(s) of refraction," and "law(s) of multiplication of species." It is this kind of talk about laws of nature which Ruby declares to be "indistinguishable from ours." 59 The problem with Ruby's approach is that it fails to note the

significant difference-for

late medieval, Renaissance, and even

the mathematical sciences and early modern thinkers-between natural philosophy. It is this presumed fundamental difference

which militates against any easy claims that laws of nature in the mathematical tradition were indistinguishable

from our present-

56 Ruby, "Origins," 352. 57 Ibid., 353, 354. Birth of History and Philosophy of Science, 240. According to Jardine s Jardine, the heavenly bodies were held to move in accordance with leges motuum prescribed by God at the Creation. This doesn't sound very far removed from the loose use of laws of nature to refer to regularities. 59 Ruby, "Origins," 343. Ruby provides numerous specific citations to Bacon's works in her footnote at this point.

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day conception of physical laws. More to the point, this difference also casts doubt on the implicit claim of Ruby's paper that mathematical laws gave rise to the later physical laws, simply by being carried over into natural philosophy. According to the Aristotelianism prevailing among scholastic natural philosophers, mathematics was essentially irrelevant to natural philosophy, because it did not, could not, deal with physical causation, and so could not provide the kind of physical explanation in terms of causes which was the aim of natural philosophy. Although optics and astronomy, and a number of other mathematical sciences, clearly dealt with physical phenomena, because they used mathematical assumptions and procedures, they were considered by Aristotle to be subordinate to the higher discipline of mathematics, not physics. Given the supposed inadequacy of mathematics for providing understanding of physical phenomena, this meant that astronomy, optics, and the other mathematical sciences, were also regarded as inferior to physics.60 Now, this state of affairs was changing during the late Renaissance period, as the certainty and practical usefulness of the mathematical sciences became increasingly recognized, and as Aristotelian natural philosophy began to appear to be increasingly fallible and misconceived. In an historical reversal of fortunes which was to have tremendous consequences, natural philosophy came to be seen as speculative and uncertain while the certainties of mathematics came to be seen as capable of providing adequate explanations for the nature of things. As early as 1540, Georg Rheticus declared in his Narratio Prima of Copernicus's system that the motion of the earth had to be decided "not by plausible opinions [in natural philosophy] but by mathematical laws."''61And it is well known that the gradual acceptance of the Copernican theory went hand in hand with the new belief that mathematics was, in spite of Aristotle, sufficient to reveal and demonstrate physical truths.62 Nevertheless, it would be wrong to see laws of nature as For a fuller discussion of these matters see Dear, Discipline and Experience; 60 Nicholas Jardine, "Epistemology of the Sciences," in Charles B. Schmitt and Quentin Skinner (eds.), The Cambridge History of Renaissance Philosophy (Cambridge, 1988), 685-711; Richard D. McKirahan, Jr., "Aristotle's Subordinate Sciences," British Journal for the History of Science 11 (1978), 197-220; and James G. Lennox, "Aristotle, Galileo, and 'Mixed Sciences'," in William A. Wallace (ed.), Reinterpreting Galileo (Washington DC, 1986), 29-51. 61 Edward Rosen, Three Copernican Treatises (New York, 1939), 393, quoted in Ruby, "Origins," 357. 62 Westman, "The Astronomer's Role." There is now an extensive literature on

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mathematicians' concepts that were simply imported into natural philosophy. In spite of Ruby's best efforts, the evidence suggests that laws of nature developed in the sixteenth and seventeenth centuries as part of the process of working out just how abstract mathematics could be said to relate to the physical world. This process was conducted by natural philosophers as much as by mathematicians. "All the familiar modern uses of 'law' were in place" by 1540, Ruby declares, but "they did not yet have their eventual currency.""6 It was, she admits, the laws of nature of Descartes's Principia philosophiae, and of Newton's Principia mathematica, which were to have "a generality and a force unmatched in the uses so far dealt with [by mathematicians]."164 As an example we can consider the law of refraction. The earliest statement of a law of refraction is found in Robert Grosseteste's De iride (ca. 1235), but here the law is simply a geometrical description: the amount a ray of light is refracted is determined by bisecting the angle the incident ray makes to the normal. The only explanation given for this is that light obeys the principle of economy and takes the shortest path possible. This is not an explanation in terms of physical causes. By the beginning of the seventeenth century, however, mathematicians like Thomas Harriot and Johannes Kepler were trying to develop physical explanations to fit in with their geometrical analyses. When Descartes discovered the law of refraction sometime between 1626 and 1629, he tried to show the reasons for the geometrical behaviour by analogy with a tennis ball breaking through a thin cloth, representing the surface of the refracting body, and having its speed altered.65 The process is not one of turning a geometrical law into a physical law but one of seeking for physical explanations to make sense of a geometrical law. the rise of the intellectual status of mathematics. See, for example, Paul Lawrence Rose, The Italian Renaissance of Mathematics: Studies on Humanists and Mathematicians from Petrarch to Galileo (Geneva, 1975); Mario Biagioli, "The Social Status of Italian Mathematicians, 1450-1600," History of Science 27 (1989), 41-95; Peter Dear, Discipline and Experience. 63 Ruby, "Origins," 357. 64 Ibid. 65 See Gaukroger, Descartes: An Intellectual Biography (Oxford, 1995), 139-46; William R. Shea, The Magic of Numbers and Motion: The Scientific Career of Rene Descartes (Canton, Mass., 1991), 156-7;John Schuster, "Descartes opticien: The Construction of the Law of Refraction and the Manufacture of its Physical Rationales, 1618-1629," in Stephen Gaukroger, John Schuster, and John Sutton (eds.), Descartes' Natural Philosophy (London, 2000), 258-312.

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This brings us to the end of our survey of the three major claims about the origins of "scientific" laws of nature in recent historiography. Let us recapitulate to see where we are. Zilsel insists that the concept of laws of nature appeared only in the seventeenth century, at first in the work of Descartes, and that this was a result of the development of the politics of absolute monarchy, incipient capitalism and the concomitant recognition of the importance of the work of artisans and craftsmen. Zilsel notices hints of laws of nature in the Middle Ages but dismisses these as merely the accidental result of theologians' thinking about "the impenetrable providence of God," which for Zilsel must be, prima facie, irrelevant. Oakley and others, by contrast, point out that by dismissing the relevance of medieval discussions of providence, Zilsel is closing off the path to discovering the origins of laws of nature. These writers have no difficulty showing the continuity between the providential theology of various medieval writers and the theological discussions raised in connection with laws of nature by Descartes, Hobbes, Boyle, Newton, Leibniz and others. Since the seventeenth-century natural philosophers turn to theology to establish the truth of laws of nature, it seems clear, Oakley and his fellow travellers argue, that the origins of laws of nature are to be found in medieval discussions of providence. Finally, we have Ruby arguing that the notion of precise laws of nature did originate in the Middle Ages, but not in discussions of "divine legislation" (which, like Zilsel, she sees as irrelevant), but in the use of a Euclidian axiomatic method in subordinate mathematical sciences which is subsequently translated into natural philosophy. Descartes and the Importance of Laws of Nature It seems perfectly clear that all three of these differing approaches bring something important to our understanding of the origins of laws of nature. We cannot eliminate any one of them without losing valuable information. By the same token, it is equally clear that none of them are sufficient on their own to provide the full story. Zilsel and Ruby are clearly wrong to dismiss the theological background as an irrelevance, but Oakley, Milton, Crombie and Funkenstein go too far in their claims for the theological origins of laws of nature. There is little or no talk of laws of nature in the original medieval discussions of God's providence they examine;

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it is the seventeenth-century thinkers who bring these medieval debates to bear upon the essentially new notion of laws of nature. Nevertheless, it seems to me that Amos Funkenstein provides the key to understanding the transformation of laws of nature from a loose metaphor in general use, or a restricted statement of principle in mathematics, to a specific explanatory proposition in natural philosophy. This key is provided in the Introduction to Funkenstein's magisterial Theology and the Scientific Imagination (1986). Introducing the theme of his book, which might be said to be the theological principles of seventeenth-century natural philosophy, Funkenstein writes: A new and unique approach to matters divine, a secular theology of sorts, emerged in the sixteenth and seventeenth centuries to a short career. It was secularin that it was conceived by laymen for laymen. Galileo and Descartes, Leibniz and Newton, Hobbes and Vico were either not clergymen at all or did not acquire an advanced degree in divinity. They were not professional theologians and yet they treated theological issues at length. Their theology

was secular also in the sense that it was oriented

toward the world, ad se-

culum.The new sciences and scholarship, they believed, made the traditional modes of theologizing obsolete; a good many professional theologians agreed with them about that. Never before or after were science, philosophy, and theology seen as almost one and the same occupation.66

Shortly after these opening words, Funkenstein insisted that this secularization of theology was "a fact of fundamental social and cultural importance," and he went on to indicate briefly how it might have come about. These indications, however, all depend upon what he calls the "erosion" of "protective belts" around theology. The implication of Funkenstein's discussion is that once these protective belts are breached, laymen will enter into theology quite naturally.67 I do not consider this to be a sufficiently convincing explanation of a historical phenomenon of such "fundamental social and cultural importance." It is my contention that the real stimulus towards the development of a secular theology, which was to change the character of natural philosophy, if only for a "brief career" in the Scientific Revolution, was the need to justify the concept of laws of nature, with its awkward inherent implication that inanimate bodies are somehow capable of "obeying" such laws. If this is correct, it allows us to combine the three historiographical rivals for the origins of laws of nature, accepting their Funkenstein, Theology, 3. 67 Ibid., 4, 4-6.

66

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best features, and omitting their misconceptions. Descartes, writing not so much as a post-Bodin Frenchman inspired by absolute monarchy (as Zilsel would have it), but as a mathematician in the forefront of efforts to develop the new physico-mathematics proposes precise laws of interaction in physics (inspired, as Ruby might have said, by the use of laws in the subordinate mathematical sciences). Almost immediately, however, Descartes realizes he is now playing a somewhat different game. While putative laws in the abstract system of mathematics needed no justification beyond their definition, the new physical laws that he was proposing needed a metaphysical underpinning. In pursuit of this new metaphysics, Descartes had to consider the nature of God's interactions with the world and turned, accordingly, to traditional providentialist theology. By claiming this theology led to the concept of laws of nature, Oakley, Funkenstein and their fellow travellers were putting the cart before the horse: in fact, the theology was taken up in order to make sense of, and to persuade contemporaries of the validity of, the concept of laws of nature. In short, therefore, we can say that Zilsel was right about the pivotal importance of Descartes in single-handedly formulating the modern concept of laws of nature, but he was wrong about the reasons for this. The two medievalist views, the theological and the mathematical, each went too far in claiming to provide the origins of the modern notion of laws of nature, but both uncover essential aspects of the historical background. There are a couple of things implicit in this account which I want to make explicit. Firstly, it should be recognized that the laws of nature are the lynch-pin of Cartesian and other mechanical philosophies. All explanations in the mechanical philosophy depend upon the interactions of moving particles of matter; the laws of nature stipulate precisely how pieces of moving matter can and do interact; therefore, all explanations in the mechanical philosophy derive from the laws of nature.68 In some respects this hardly needs saying; it is perfectly obvious that the laws of nature are the foundations upon which Descartes builds his kinematic physics.69 In 68 This is summed up in articles 199-203, in Part IV of the Principia philosophiae. See also Friedrich Steinle, "Amalgamation of a Concept," 336-7; and Stephen Gaukroger, Descartes' System of Natural Philosophy (Cambridge, 2002), 13-14, 18-19 eschewed the use of forces in his conception of 69 Like Galileo, Descartes physics and sought to explain everything in terms of motion and impact (forces of impact where the only forces considered to be intelligible and legitimate). See

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spite of the obviousness of this, however, or indeed perhaps because it is so very obvious, accounts of Descartes's philosophy all too often discuss the laws as though in passing, or late in the account instead of at the outset, or simply without drawing sufficient attention to their seminal importance.70 Secondly, if the laws were to be seen as legitimate aspects of natural philosophy, they had to serve an explanatory, not merely a descriptive, function. It should be noted, for example, that the incursions of mathematicians, and their mathematical ways, into natural philosophy did not negate the traditional natural philosophical concern with explanation, but merely tried to extend it to accept certain mathematical proofs as explanatory in themselves. In some cases, of course, this could only be achieved by taking contemporary natural philosophers through intermediary positions. Johannes Kepler saw his archetypes (geometrical and musical), for example, as the indirect way to convince doubters of the utility of mathematics for revealing physical truth. Accepting that mathematics could not establish physical causes, Kepler insisted it could reveal a divine "archetype"; that archetype could then provide the causal account missing from the mathematics itself. Archetypes, he wrote in Mysterium cosmographicum(1597) "are the cause of natural things." Yet "they would have possessed no force," he continued, "if God himself had not had regard to Gary Hatfield, "Force (God) in Descartes' Physics," Studies in History and Philosophy of Science 10 (1979), 113-40; Daniel Garber, Descartes'Metaphysical Physics (Chicago, 1992), 293-9; Dennis Des Chene, Physiologia: Natural Philosophy in Late Aristotelian and Cartesian Thought (Ithaca, 1996), 312-41; Patrick Suppes, "Descartes and the Problem of Action at a Distance," Journal of the History of Ideas 15 (1954), 146-52; and John Henry, "Galileo, Descartes, and the Importance of Kinematics," in Juan Jose Saldafia (ed.), Science and Cultural Diversity. Proceedings of the XXIst International Congress of the History of Science, Mexico City, 7-14 July 2001 (Mexico, D. F., 2004?), in press. 70 It is always unfair, of course, to criticize other authors for failing to share one's own preoccupations, so with apologies I merely cite in support of this claim three recent major studies on Descartes's natural philosophy. Shea, Magic of Numbers and Motion, brings the laws of motion into his account in a sub-section of Chapter 11, 269-73 (the subsequent chapter entitled "The Laws and Rules of Motion," 279-315 is chiefly concerned with vortex theory and other aspects of the system, though there is a sub-section on the collision rules, 295-99). Daniel Garber, Descartes' Metaphysical Physics, brings the laws into play in chapters 7-9, 197305 (at least they get a very full treatment). Gaukroger, in his Descartes:An Intellectual Biography, introduces the laws of motion in a sub-section of chapter 7, 237-49. I note also that there is no article devoted to the laws of nature in Gaukroger, Schuster and Sutton (eds.), Descartes' Natural Philosophy, although Peter McLaughlin's "Force, Determination and Impact," 81-112, comes close, and provides excellent new insights.

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them in the act of Creation." So, while mathematics itself is insufficient to reveal physical causes, by revealing an archetype, it shows that God caused the physical world to conform to the mathematics.71 Accordingly, if Descartes sought to base his new philosophical system, at least in principle, on three laws of nature, they had to be explanatory laws, not just mathematical rules, nor shorthand expressions for regularities in nature. In other words, the laws had to codify the nature of causation in the Cartesian universe. It would not have taken Descartes long to realize that he could not claim causal efficacy for his laws without invoking God, and hence his turn to the theology of providence, and a thorough concern with the metaphysical underpinning of his natural philosophy. I believe there is circumstantial evidence for my view of the pivotal importance of laws of nature in Descartes's philosophy (if any is required) in the well-known details of Descartes's intellectual biography. It is generally acknowledged that Descartes started out as a mathematician, and began to consider natural philosophy only after his chance meeting with Isaac Beeckman in November 1618, when he took up the enterprise of physico-mathematics. Before long, however, he entered seriously into the realm of metaphysics, thereby guaranteeing his place in the philosophical canon, long after his natural philosophy was discreditied. It is important for our purposes to know when and why Descartes took up metaphysics. There is no explanation for Descartes's move into metaphysics in what might be regarded as mainstream philosophical literature-it is as though Descartes took up metaphysics simply because he was deeply thoughtful. In order to discover discussions of this point we need to look at those historians of philosophy who have recognized the importance of seeing Descartes as a natural philosopher seeking to replace Aristotelian natural philosophy with a more accurate account of the physical world.72 Such historians of 71Johannes Kepler, The Secretof the Universe, translated by A. M. Duncan (New York, 1981), 125; or Johannes Kepler, GesammelteWerke,edited by V. W. Dyck, M. Caspar, and F. Hammer, 21 vols. (Munich, 1937-2002 ), 8: 62. For a full account of this, see Rhonda Martens, Kepler'sPhilosophy and the New Astronomy (Princeton, 2000), especially 109. Bernard 72 Daniel Garber has pointed out, for example, that the philosopher Williams has drawn a distinction between "historians of ideas" for whom historical context is paramount, and historians of philosophy, for whom "articulating philosophical ideas" is paramount: Bernard Williams, Descartes: The Project of Pure Enquiry (Harmondsworth, 1978), 9-10. Preferring the second approach, Williams

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philosophy are generally agreed that Descartes turned to metaphysics to back up his physics. Gary Hatfield, who discerns what he calls a clear "metaphysical turn" in Descartes's career, suggests that this is "best understood in the context of Descartes's attempts to provide secure foundations for his physics." He goes on, however, to see this entirely in terms of a "reformulated theory of the human intellect and its objects."" Hatfield locates the metaphysical turn around 1628 or the following year. Stephen Gaukroger, by contrast, sees Descartes's interest in metaphysics beginning only in 1633, after Descartes heard of the condemnation of Galileo and felt obliged to suppress his Le Monde. At this point in his career, according to Gaukroger, Descartes's "creative period in natural philosophy comes to an end, and a creative period in legitimatory metaphysics begins." Like Hatfield, however, Gaukroger also considers the main focus of the metaphysics to be "the question of the legitimation of knowledge in a new and radical way."74 It is worth considering what we know of Descartes's "metaphysical turn" from the historical sources. In my view, there is no hint of any metaphysical concern in Descartes's correspondence until the letter to Mersenne written at the end of 1629. On the face of it, the stimulus seems to be, as Gaukroger would have wished it, an anxiety about possible religious opposition to the doctrines of Le Monde. Having said that he does not want to publish his system until it has been scrutinized by Mersenne and other trustworthy readers, Descartes writes: "I wish this mainly on account of theology, which has been so deeply in the thrall of Aristotle that it is almost impossible to expound another philosophy without its seeming to be directly contrary to the Faith." It is at this point that himself reconstructs Cartesian thought in a way deemed interesting for a twentieth-century philosophical audience. See Daniel Garber, Descartes Embodied: Read2001), 4-5. ing Cartesian Philosophy through Cartesian Science (Cambridge, Admittedly, the number of philosophers who take Descartes's natural philosophy seriously is now growing apace, but for a while there were only Garber, Stephen Gaukroger, Gary Hatfield and Roger Ariew, at least in the Anglophone world. 17 Gary Hatfield, "Reason, Nature and God in Descartes," in Stephen Voss (ed.), Essays on the Philosophy and Science of Rene Descartes (Oxford, 1993), 259-87, 259. See also the same author's Descartes and the Meditations (London, 2003), 157. 74 Gaukroger, Descartes, 292. Garber, in his Descartes' Metaphysical Physics, does not really address this issue. He simply designates metaphysics as one of Descartes's first projects (16). It is evident that Gaukroger regards Descartes's Principia philosophiae (1644) as essentially a systematic re-statement of the natural philosophy of Le Monde, combined with his subsequently developed metaphysics.

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he indicates that he now feels the need to stray out of natural philosophy: Apropos this topic, please tell me whether there is anything definite in religion concerning the extension of created things, that is, whether it is finite or infinite, and whether in all these regions called "imaginary spaces" there are genuine created bodies. Although I was not keen to touch on this topic I believe nevertheless I shall have to go into it...75

The same letter contains more on God, but we'll return to this shortly. First, it is worth pointing out that for Descartes such issues are to be considered metaphysical, not just theological. This is clear from a subsequent letter to Mersenne: Your question of theology is beyond my mental capacity, but it does not seem to me outside my province, since it has no concern with anything dependent on revelation, which is what I call theology in the strict sense; it is a metaphysical question which is to be examined by human reason.76

It is in this same letter where we find the hint which I presume led Gary Hatfield to suppose that the major issue in Descartes's metaphysics was a theory of the human intellect. It is sufficiently important to merit quotation in full. I think that all those to whom God has given the use of this [sc. human] reason have an obligation to employ it principally in the endeavour to know him and to know themselves. That is the task with which I began my studies; and I can say that I would not have been able to discover the foundations of physics if I had not looked for them along that road. It is the topic which I have studied more than any other and in which, thank God, I have not altogether wasted my time. At least I think that I have found out how to prove metaphysical truths in a manner which is more evident than the proofs of my opinion, that is: I do not know if I shall be able to congeometry-in vince others of it. I think that you heard me speak once before of my plan to write something on the topic; but I do not think it opportune to do so before I have seen how my treatise on physics is received..."77

On the face of it, then, we have clear support here for Hatfield's view of the why and when of the "metaphysical turn." He took this Descartes to Mersenne, 18 December 1629, quoted from J. Cottingham, R. 75 Stoothoff, D. Murdoch and A. Kenny (eds.), The Philosophical Writings of Descartes, Vol. III: The Correspondence(Cambridge, 1991), 14. Hereafter cited as Correspondence. See also: Charles Adam and Paul Tannery (eds.), (Euvres de Descartes: Correspondance, 5 vols. (Paris, 1974-76), 1:86. Hereafter cited in parentheses after the reference to the English edition, in the form: AT 1:86. We will not pursue the answer to Descartes's questions here, but for those who are interested, see Edward Grant, Much Ado About Nothing: Theoriesof Space and Vacuumfrom the Middle Ages to the Scientific Revolution (Cambridge, 1981). to Mersenne, 15 April 1630, Correspondence,22 (AT 1:143-4). 76 Descartes 77 Ibid. (AT 1:144)

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turn as soon as he arrived in Holland late in 1628, and he did so in order to know God and to know himself, which we might perhaps interpret as a reference to a quest to understand the intellect. Furthermore, Descartes is sufficiently proud of his achievements that he sees them as emulating the certainty of geometry. If we read on, however, this letter also offers support for my contention that the concept of specific laws of nature led Descartes to turn to metaphysics: in my treatise on physics I shall discuss a number of metaphysical topics and especially the following. The mathematical truths which you call eternal have been laid down by God and depend upon him no less than the rest of his creatures. Indeed to say that these truths are independent of God is to talk of him as if he were Jupiter or Saturn and to subject him to the Styx and the

Fates. Please do not hesitate to assert and proclaim everywhere that it is God who has laid down these laws in nature just as a king lays down laws in his kingdom. There is no single one that we cannot grasp if our mind turns to consider it. They are all inborn in our minds just as a king would imprint his laws on the hearts of all his subjects if he had enough power to do so.78

To be sure there is a concern here, at the end, with the certainty of our knowledge. Descartes wants to insist that the laws he has seen to be operating in the physical world cannot be dismissed as mere opinions or theoretical constructs of his, but are undeniable to any right-thinking person. So, we do see the beginnings of Descartes's thinking about intuitions, clear ideas, and so forth. These ideas are called upon, however, to support the notion that the world can be understood in terms of laws of nature. Admittedly, there are some difficulties in the interpretation of this passage. Descartes begins by discussing the "mathematical truths," presumably taking issue with something said in Mersenne's no longer extant letter about them being eternal truths. When he mentions "these laws of nature," therefore, it looks as though he is simply using the term in the way it was used in the mathematical tradition to refer to mathematical, and by extension other supposedly "eternal," truths. There is an extensive literature on the concept of eternal truths in Descartes, but we need not pursue that 78 Ibid., 22-3 (AT 1:145). On the eternal truths see also the letters to Mersenne dated 6 May and 27 May, 1630, Correspondence,24-6 (AT 1:148-54). For considerations of the importance of God's creation of the eternal truths see Funkenstein, Theology, 179-192; Emile Brehier, "The Creation of the Eternal Truths in Descartes's System," in Willis Doney (ed.), Descartes: A Collection of Critical Essays (Notre Dame, 1968), 192-208; and Etienne Gilson, La liberte chez Descartes et la theologie (Paris, 1982); and Jean-Luc Marion, Sur la theologie blanche de Descartes: Analogie, creation des verites eternelles et fondement (Paris, 1981).

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here.79 For our purposes, the important thing is whether this passage can be taken as evidence for my claim that Descartes first turned to metaphysics as a way of legitimating his notion of physical laws of nature. It might be said, for example, that in this reference to laws of nature, Descartes simply has in mind something like the "law"that the angles of a triangle must add up to two right angles."80

It cannot be said, however, that at this time Descartes had not yet formulated a notion of physical laws of nature. On the contrary, it is perfectly clear from earlier letters to Mersenne that Descartes was already working with versions of at least one of the laws he was to set down in Le Monde. Even in the letter in which Descartes first announces to Mersenne that he is writing a treatise "to explain all the phenomena of nature, that is to say, the whole of physics" (November 1629), he makes use of something like his first law while explaining acceleration due to gravity: "I make the assumption that the motion impressed on a body at one time remains in it for all time unless it is taken away by some other cause; in other words, in a vacuum that which has once begun to move keeps on moving at the same speed."81 What is more, in this same letter, Descartes returns to an account of the motion of a pendulum which he provided in his letter of 8 October. It is clear that Descartes was already using something like his first law in October, even though he only clarifies that for Mersenne in the November letter: As for your question concerning the basis of my calculation of the time it takes the weight to fall when it is attached to a cord 2, 4, 8 and 16 feet long as the case may be, I shall have to include this in my Physics. But you should not have to wait for that; so I shall try to explain it. Firstly, I make the assumption that the motion impressed on a body at one time remains in it for all time unless it is taken away by some other cause; in other words, in a vacuum that which has once begun to move keeps on moving at the same speed.82

On the eternal truths see references in preceding note. so This would fit perfectly, for example, with Jane Ruby's claims about the origin of the concept of laws of nature. See Ruby, "Origins." 81 Descartes to Mersenne, 13 November 1629, Correspondence,7, 8 (AT 1:70, 71). to his Physics is clearly a 82 Ibid., Correspondence,8 (AT 1:71). The reference reference to the forthcoming Le Monde. It is interesting to note that Descartes has not yet committed himself to plenism, although while discussing another problem later in the same letter (the motion of a plucked string), the plenist alternative, linked to a concomitant circularity of movement, as in the vortexes, dawns on him: 'Yet I am not sure about this; perhaps on the contrary the air even aids 79

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The same law is invoked again in connection with free fall in the letter of 18 December 1629, and again in explaining the rebounding of a ball in letters in January and February 1630.83 It seems to me, therefore, that there is sufficient evidence in these early letters to Mersenne to show that Descartes had already seen how to explain natural phenomena in terms of physical laws of nature, and this was to be the mainstay of his Physics, or of his Le Monde. Moreover, his urgent call to Mersenne, in April 1630, not to "hesitate to assert and proclaim everywhere that it is God who has laid down these laws in nature," can only derive from Descartes's concern to persuade his contemporaries of the legitimacy and importance of his physical laws of nature. It seems hard to imagine why Descartes would think it was "especially" important to discuss the metaphysics underlying the Euclidean claim that the angles of a triangle add up to two right angles, much less why he would want Mersenne to continually proclaim this. (Presumably Descartes is concerned about how Mersenne is going to pass on to his other correspondents what he is doing). It is not hard to see, however, why he might regard it as important to discuss the metaphysics underlying what he could quite justifiably consider to be a completely new conception in natural philosophy, namely, physical laws of nature.84 It is also easy to see why he might have conflated his thinking about such laws with mathematical "laws," or "truths," at least in a letter to Mersenne written before he has arrived at his final position, given that the original model for his thinking is likely to have been geometrical optics or one of the other mixed mathematical sciences.85

the motion at the end, since the motion is circular" (ibid., 10; AT I: 74). I take this to be an example of how the letters provide hints towards Descartes's thought processes, which I am trying to exploit here. 83 Descartes, Correspondence,15, 17, 18-19 (AT 1:89-90, 107, 117). 84 It should be noted that, as various scholars have pointed out, many of the now famous "laws" discovered during the Scientific Revolution have only been designated as laws retrospectively and would not have been thought of as laws of nature by Descartes. So, Galileo's law of free fall, for example, and Kepler's laws of planetary motion were not known as laws until after the appearance of Descartes's laws. See Milton, "Origin and Development"; Steinle, "Amalgamation of a Concept," 320-1; J. L. Russell, "Kepler's Laws of Planetary Motion: 1609-1666," British Journal for the History of Science 2 (1964), 1-24. It seems 85 Again, this last suggestion is in accordance with Jane Ruby's views. a highly plausible reconstruction of Descartes's thinking, given that he also (though perhaps later) reduced material bodies to extension to enable him to imply that body was completely quantifiable. See Funkenstein, Theology, 183-4.

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It seems clear, therefore, that Descartes began to think of the necessity for a metaphysical underpinning to his new physics as he was writing Le Monde. Furthermore, as the letter of 15 April 1630 suggests, an especial aspect of the metaphysics was directly linked to his thinking about laws of nature. Announcing what metaphysical topics he will discuss he mentions only God's creation of the mathematical truths, before calling upon Mersenne to "proclaim everywhere" that God has created the laws of nature. This view seems to be confirmed even by a superficial glance at Le Monde itself. The opening four chapters familiarize the reader with a corpuscularian universe, in which all bodies are composed of invisibly small particles and all change is brought about by movement and reorganization of the constituent particles. Chapter 5 sets the seal on this by defining the three kinds of particles (differing in size and shape) which are designated as "elements." God, and we might say metaphysics, appears for the first time in Chapter 6, where Descartes sets up, for the kind of theological reasons alluded to in his letter to Mersenne of December 1629 (where theology is declared to be in the thrall of Aristotle), the notion that what follows is only a fable of a world "in which there is nothing that the dullest mind cannot conceive, and which nevertheless could not be created exactly the way I have imagined it."86 It is only in the next chapter that God, or metaphysics, begins to play an active, and indispensable, role in the new physics. Descartes indicates that the foregoing chapters have all been merely preamble, but now "I do not want to delay any longer." He wants to tell us "what the laws of Nature that God has imposed on it [Nature] are."87As well as outlining the laws, Descartes also repeatedly tells his readers about the immutability of God and his conserving power, and even, that "we must say that God alone is the author of all the motions in the world in so far as they exist and in so far as they are straight."88 I believe that Gaukroger's suggestion that Descartes only turned to metaphysics after he noticed the need for theological justification in the wake of the Galileo affair fails to take seriously the metaphysical problems inherent in a physics based upon precise laws of nature by which God is said "to cause the nature of this new 86 Rene Descartes, The World and Other Writings, translated and edited by Stephen Gaukroger (Cambridge, 1998), 24. 87 Ibid., 24-5. 88 Ibid., 30, see also 25, 28, 29, 31, 32.

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world to act."89Even without entering into an argument about the vigour and consistency of Descartes's philosophical acuity, we can see from the historical evidence that the nature of the laws of nature themselves forced Descartes to confront what he called "metaphysical considerations.""90 Similarly, I remain unconvinced by Hatfield's suggestion that the metaphysical turn stemmed from the hyperbolic doubt used not only paradoxically to guarantee certain truths (as in the Discourse on the Method), but also to demonstrate to the reader the proper function and objects of the intellect, in particular that the pure intellect, withdrawn from the senses, is capable of clear and distinct intuitions about the existence of God and the soul, and the essence of material things (as in the Meditations).91

I have no difficulty with the substance of Hatfield's thesis, which seems to me to provide a truly illuminating account of the mature metaphysics as it related to Descartes's physics. My objection is simply that the historical evidence, such as it is, suggests that these highly sophisticated metaphysical ideas were developed later, after Descartes had already been led by something else to turn, as a novice, to metaphysical considerations. This remains true, notwithstanding Descartes's claim to Mersenne in 1637, quoted by Hatfield, that he wrote "the beginnings of a treatise of metaphysics" dealing with the immateriality of the soul eight years before, which would be 1630.92 Certainly this tallies with the letter of 15 April of that year, in which Descartes links the foundations of his physics to "the endeavour to know [God] and to know themselves," but it is difficult to imagine that Descartes had at this time more than an inkling (albeit a brilliant one) of what he would not fully work out until 1640.93 Daniel Garber suggests that the "metaphysics of Discourse IV, a preliminary sketch of the Meditations, represents a later Ibid., 25. Gaukroger, Descartes, 292. Ibid. I am taking for granted here, as Gaukroger and Hatfield do, that Descartes has not yet formed the ambition to replace the whole of scholastic philosophy. Had he already done so, there would be no need to explain why he should include metaphysics in his scheme, since metaphysics was a major aspect of scholastic philosophy. It seems clear from his correspondence and the nature of his early writings, however, that Descartes saw himself first of all as a mathematician, then a physicist, and natural philosopher, and only subsequently formulated the idea of completely superseding Aristotle. 91 Hatfield, "Reason, Nature and God," 262-6. 92 Descartes to Mersenne, 27 February 1637 [or end of April 1637?], Correspondence, 53 (AT 1:350). "3Garber, Descartes' Metaphysical Physics, 17. 89 90

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stage in his thought," and that we cannot know what the early writings on metaphysics may have contained. He does note, however, that the early metaphysics is "clearly connected with his physics." It seems to me, therefore, that Hatfield has undoubtedly revealed the direction that Descartes's metaphysical speculations took, but he does not satisfactorily explain why Descartes turned to metaphysics in the first place (or, indeed, at all).94 I believe the answer to this problem lies in the formalities of Descartes's physics, and in particular in its innovatory use of physical laws of nature. Nobody is in any doubt, after all, that Descartes's physics preceded his metaphysics. When Descartes told Mersenne that his six Meditations contained "all the foundations of his physics," the sense that the metaphysics was written in order to support the physics is reinforced by Descartes's request that Mersenne keep this under his hat. It seems clear that Descartes believed his ideas on God and the soul had a better chance of succeeding if their service to his physics was not known. It seems equally clear, however, that his ultimate aim was to see his natural philosophy established.95 I want to suggest, then, that there are sufficient grounds in the concept of laws of nature, as Descartes conceived them, to force him to consider the role of God in his physics, and therefore to set him off on what he called "metaphysical considerations" and what Funkenstein saw as his "secular theology." We can see in the account Descartes gives of them in both Le Monde and the Principia that the laws of nature are bound up with the distinction of matter into separate parts. In Le Monde, for example, Descartes asks his readers to imagine the universe filled with matter-not the 94 Few other writers on Descartes seem to consider this question at all. Most historians of philosophy, as far as I can tell, simply take it for granted that a genius of Descartes's calibre would turn to metaphysics, and confine themselves to discussing when he did so. In so far as any reason for the metaphysical turn is given it usually hinges upon Descartes meeting with Cardinal Berulle, who encouraged Descartes's philosophical studies (which is usually taken to imply metaphysical studies, but I can't see why), which Baillet reports as taking place late in 1628, but which Genevieve Rodis-Lewis suggests took place in November 1627. Genevieve Rodis-Lewis, Descartes, His Life and Thought, translated by Jane Marie Todd (Ithaca, 1998), 66-7. 95 Mersenne to Descartes, 28 January 1641, Correspondence, 173 (AT 3:298). Hatfield also acknowledges the role of the metaphysics in providing contemporary readers with would-be persuasive foundations for the physics. Hatfield, "Reason, Nature and God," 265-6.

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prime matter of the Aristotelians which has no reality without form, and which Descartes considers to be incomprehensible, but matter which constitutes "a real, perfectly solid body, which uniformly fills the entire length, breadth, and depth of this great space." Evidently this is not the way things are, so Descartes asks us to imagine this great body to be broken up into parts. He is careful to insist, however, that the parts are not divided from one another by being separated in space, so that there would be void between them. The differences between the parts of matter are discernable by, one might even say defined by, a diversity in their motions. Here then we have the two major principles of the mechanical philosophy: matter and motion. Without motion in the system, there could be no differentiation between the parts of matter, since all matter is uniform and fills all of space, thus creating a uniform continuum. As soon as motion is introduced into the account, so are the laws of nature. "From the first instant of their creation," he says, referring to the parts of matter defined by their movements, "He causes them to continue moving thereafter in accordance with the ordinary laws of nature." Descartes now declares that these laws have been so well contrived by God that nothing further is required to explain how our world comes about: the result will be "a world in which one will be able to see not only light, but all the other things as well, both general and particular, that appear in the actual world."96 Clearly God is built-in to the Cartesian account, but the question arises, does He have to be? Could Descartes have offered an atheist version of his physics? We know that atheist versions of the Cartesian philosophy were soon to appear in the seventeenth century, so might not Descartes himself have excluded God from his concerns? The nature of historical argument does not allow us to 96 Descartes, World, Chapter 6, 23. Cf. Principia philosophiae, II, ?36. The production of our world requires not just the laws of nature but the right starting conditions, this is implicit in the account. It also hinges upon the immutability of God which is introduced in the next chapter of Le Monde when the laws are discussed in detail, and mentioned immediately in the Principia, II, ?36. Presumably when Descartes talks of the "ordinary laws of nature" he means to imply that these are what we are familiar with, albeit unconsciously, from everyday phenomena. There may be an echo here of the theological distinction between God's potentia ordinata and His potentia absoluta; the latter being responsible for miracles and other exceptional events, while the former was held to be responsible for maintaining the ordinary concourse of events. See the quotation from Robert Boyle at note 107 below; Oakley, Omnipotence, Covenant and Order, 67-92; and Funkenstein, Theology, 124-52.

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say that an atheist Descartes would have been impossible, but it seems abundantly clear that subsequent atheist versions of the mechanical philosophy were only historically possible as a result of the enormous impact, and subsequent influence, of the Cartesian system.97 Once Descartes had shown how the system worked, and how it was possible, in principle at least, to explain all the phenomena of nature in terms of matter moving in accordance with laws of nature, it was easy for the atheist to appropriate the system.98 At the moment of their first formulation, however, laws of nature would have been unintelligible and untenable, unless they were underwritten by God. The reason for this unintelligibility was precisely because Descartes wanted to claim that the laws of nature operated as causes. It is hard for us today (in spite of David Hume) not to think of Newton's laws as causes of physical phenomena (Newton being our Descartes), but for contemporaries of Descartes his laws were so unfamiliar, and so unlike the kinds of causes usually discussed in natural philosophy, that the opposite was true. Part of the problem was the austerity of the Cartesian scheme. Scholastic causal explanations tended to be couched in terms of the active powers of one or other of the interacting things. The power in question, of course, was all too often simply defined in accordance with the dormitive power of opium, as we all know, required effects-the so traditional scholasticism was already subject caused sleep-and to much criticism.99 Even so, the Cartesian system seemed to take 97 Although, right from the outset, the Cartesian system was seen to be fraught with problems, it was widely seen as pointing the way to a system of philosophy capable of replacing, lock, stock and barrel, the comprehensive systematic philosophy of Aristotelianism. Accordingly, Cartesianism was far more successful and influential than might be expected on the basis of a critical evaluation. The literature on Cartesian influence is vast but useful starting points are: Nicholas Jolley, "The Reception of Descartes' Philosophy," in John Cottingham (ed.), The Cambridge Companion to Descartes (Cambridge, 1992), 393-423; and Thomas M. Lennon, The Battle of the Gods and Giants: The Legacies of Descartes and Gassendi, 1655-1715 (Princeton, 1993). 98 Descartes claimed to be able to explain everything, not only at the outset of Le Monde (see previous note), but also at the end of the Principia, IV, ?199. 99 For a fuller discussion of these matters see Stephen Nadler, "Doctrines of Explanation in Late Scholasticism and in the Mechanical Philosophy," in Garber and Ayers (eds.), CambridgeHistory of Seventeenth-CenturyPhilosophy, 513-52. There is relevant material also in Alan Gabbey, "The Mechanical Philosophy and Its Problems: Mechanical Explanations, Impenetrability, and Perpetual Motion," in J. C. Pitt (ed.), Change and Progressin Modern Science (Dordrecht, 1985), 9-84; idem, "Mechanical Philosophies and their Explanations," in Christoph Lfithy, John Murdoch, and William Newman (eds.), Late Medieval and Early Modern Corpuscular

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things too far. According to Descartes the only cause of change in the world was collision between particles of matter. Impacts between particles, and the subsequent changes of relative positions and motions were the only explanatory resources in Cartesian physics.100 It wasn't just the austerity of this that caused problems for contemporaries. It was also highly unfamiliar to those not conversant with, say, ballistics or other aspects of the mathematical sciences concerned with forces of impact. This can be seen in an extreme form in Henry More's comment on Descartes: But he is fabricating some kind of life in that when two bodies meet, he is able to accommodate their motions so that each of them notified by the other, the one about acceleration of its motion, the other about retardation of its motion, finally agrees on the same course of motion. And it is the same thing for the other laws of transport. For Descartes himself scarcely dares to assert that the motion in one body passes into another...'•?

The problem for More here was that he still regarded motion as a mode of body (comparable to shape, another mode of body) and the traditional scholastic assumption was that modes cannot be transferred from one body to another. In his earlier correspondence with More, Descartes had actually conceded that this was the case but he escaped by referring, obliquely, to God: You observe correctly that "motion, being a mode of body, cannot pass from one body to another." But that is not what I wrote; indeed I think that motion, considered as a mode, continually changes... But when I said that the same amount of motion always remains in matter, I meant this about the force which impels its parts, which is applied at different times to different parts of matter in accordance with the laws set out in articles 45 and following of Part Two.102

In Descartes's austere world there is no force other than God, so this is a clear case of Descartes having to rely on God for the causal Matter Theory (Leiden, 2001), 441-65; and Hutchison, "Individual, Causal Location, and the Eclipse of Scholastic Philosophy." I cannot help remarking, however, that laws of nature are largely overlooked in these studies. 100 On this see McLaughlin, "Force, Determination and Impact," 86; and Steinle, "Amalgamation of a Concept," 336-7, and 356-7. 101 Henry More, "Responsio ad fragmentum Cartesii" (July/August 1655), quoted from Alan Gabbey, "Philosophia Cartesiana triumphata: Henry More (1646-1671)," in T. M. Lennon (ed.), Problems of Cartesianism (Toronto, 1982), 171-250, 212-3. See also McLaughlin, "Force, Determination and Impact," 97. 102 Descartes to More, August 1649, Correspondence,382 (AT 5:404-5). See also 381 (AT 5:403), where Descartes explicitly mentions God as the "power causing motion."

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efficacy in colliding bodies.'03 Since modes cannot be transferred, and motion is a mode of body, motions cannot be directly transferred but must be exchanged by God. Descartes's laws were also heavily dependent upon the principle of the immutability of God. Although, as Garber says, the principle "that motion in and of itself persists" was "very much in the air" when Descartes was incorporating it into his laws of nature, it was still a highly counter-intuitive notion for most thinkers.104 The Aristotelian dictum, omne quod movetur ab alio movetur, was held to be a diachronic principle; when the mover stops the action of moving, so motion ceases. There were ways of considering continued motions, by invoking the notion of impetus, for example, but the assumption was that motion would cease once an impetus was exhausted. It is hard to imagine how Descartes could have proposed the indefinite persistence of motion as a principle without immediately asking himself how this could be, much less how he could present it to the educated public without some account of what kept things in motion. The same applies, of course, for his third law and the associated rules of impact, detailing how motions are (seemingly) transferred from one body to another in collisions. The natural assumption for most people, based on experience leading to an entrenched intuition, would be that motions rapidly die away in a series of impacts. Until those intuitions changed (as perhaps they have in a post-Newtonian world?), thinkers would need to be reassured of the conservation of motion by an omnipotent God. Another problem for the Cartesian position, of course, was the intelligibility of inanimate objects obeying "laws." This is perhaps a more general aspect of the kind of ideas expressed above by Henry More, when he suggested an animistic interpretation of the behaviour of bodies in collision. At one point in the Principia Descartes specifically tried to correct this kind of thinking: When I say that these little globules strive... to recede from the around which they revolve, I do not intend that there be attributed any thought from which that striving might derive; I mean only that so situated, and so disposed to move, that they will in fact recede if not restrained by any other cause.105

centers to them they are they are

10" See Hatfield, "Force (God) in Descartes' Physics"; Garber, Descartes' Metaphysical Physics, 293-9; Dennis Des Chene, Physiologia, 312-41. 104 Daniel Garber, "Descartes' Physics," in Cottingham (ed.), Cambridge Companion to Descartes, 286-334, at 315. 105 Descartes, Principia, III, ?56

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Although Descartes does not mention God here, the attentive reader who pursued this would realize that the disposition of these globules to move centrifugally is in fact an otherwise inexplicable by-product of God's perpetual endeavour to keep them moving in a straight line. This kind of account led some of Descartes's followers, as is well known, to develop occasionalist theories in which the incessant action of God was fully acknowledged. Descartes was too much of a natural philosopher to ever fully embrace this theological position, but it is sometimes difficult to see how he managed to avoid it.'06 There was always a strong tendency, anyway, to acknowledge that the phrase "laws of nature," applied to inanimate creatures, could only be a shorthand expression for the action of God. As Robert Boyle was to insist, It is plain that nothing but an intellectual being can be properly capable of receiving and acting by a law... And it is intelligible to me that God should... impress determinate motions upon the parts of matter, and that... he should by his ordinary and general concourse maintain those powers which he gave the parts of matter to transmit their motion thus and thus to one another. But I cannot conceive how a body devoid of understanding and sense, truly so called, can moderate and determine its own motions, especially so as to make them conformable to laws that it has no knowledge or apprehension of.107

In the Principia Descartes declares that the causes of motion are twofold. God is "the general cause of all the movements in the world," but the laws of nature are the "secondary and particular causes of the diverse movements which we notice in individual bodies."108There remains a residual sense, however, in which the laws of nature in Descartes's physics are not really causes at all. They are merely descriptions of the way bodies behave, as though for use in analyzing given interactions. We can see here, therefore, their antecedents in the mathematical traditions of laws of nature which Jane Ruby has brought to our attention. It is difficult to see how Descartes could have moved from here to laws which were genuinely casual without having to take what Hatfield calls a metaphysical turn, and introducing God into his story. It is important 106 See, for example, C. J. McCracken, Malebranche and British Philosophy (Oxford, 1983); Daniel Garber, "How God Causes Motion: Descartes, Divine Sustenance, and Occasionalism," Journal of Philosophy 84 (1987), 567-80; and Garber, Descartes' Metaphysical Physics, 299-305. I explain what I mean by "too much of a natural philosopher" at the end of the paragraph. 107 Robert Boyle, A Free Enquiry into the Vulgarly Received Notion of Nature [ 1686], edited by Edward B. Davis and Michael Hunter (Cambridge, 1996), Section II, 24. 108 Descartes, Principia, II, ?36, ?37.

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to note, however, that, as a natural philosopher, Descartes could not have been content to refer all his explanations directly to God. As Edward Grant has recently reminded us in a series of important books, although natural philosophy was seen as a handmaiden to theology, it was recognized to be different from theology, and to be concerned exclusively (at least as far as possible) with naturalistic explanation.109 Bearing this in mind, we can see that it was important for Descartes to present the laws of nature as explanatory causative principles in their own right. The nature of these laws, however, demanded a unique and detailed metaphysics to justify and underwrite his new physics. Since this metaphysics depended upon the intervention of God, Descartes had to develop, as Funkenstein pointed out, a secular theology. As is well known, Descartes's laws of nature failed to capture with sufficient accuracy the phenomena of nature. Besides, many of his explanations of natural phenomena were so vague that there was no need to refer back to the laws in any explicit way. The explanations of phenomena provided in the Cartesian system looked in many respects just like those provided in ancient atomism, or in the less rigorous corpuscularianism of a Pierre Gassendi, or a Robert Boyle. Certainly, there was little sign that the founder of Cartesianism had begun as a gifted mathematician, inspired to extend the rigorous certainties of mathematics into natural philosophy."l0 Nevertheless, it remains hard to overestimate Descartes's importance for the history of science and the history of Western culture more generally. The importance of discovering the correct laws of nature exercised the greatest mathematical minds in the succeeding generations up to and beyond the publication of Isaac Newton's Principia mathematica."' After Newton it became accepted that the discovery and confirmation of laws of nature is, and should be, a defining enterprise of the hard sciences, if not of all 109 Edward Grant, Planets, Stars, and Orbs: The Medieval Cosmos, 1200-1687 (Cambridge, 1994); idem, The Foundations of Modern Science in the Middle Ages; and idem, God and Reason in the Middle Ages (Cambridge, 2001). 110 On the lack of mathematics and mechanics in Descartes's mechanical philosophy see, for example, Alan Gabbey, "Descartes's Physics and Descartes's Mechanics: Chicken and Egg?," in Voss, Essays on the Philosophy and Science of Reni Descartes, 311-23; and Daniel Garber, "A Different Descartes: Descartes and the Programme for a Mathematical Physics in His Correspondence," in Gaukroger, Schuster and Sutton (eds.), Descartes' Natural Philosophy, 113-130. 111This is another aspect of the importance of laws of nature in the Scientific Revolution, but which has also never been properly examined. I hope to make a contribution to this part of the story in another paper.

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sciences. Newton's friend David Gregory once remarked that "every Problem in terrestrial Physics is very operose and perplex'd, but on the contrary in the Celestial Physics, they are most easy and simple," and suggested, accordingly, that the "Laws of Nature are to be learn'd" most easily in astronomy."'2 He might have had in mind Descartes's noble failure, and Newton's astonishing success. Whatever the truth of this, we can certainly add that Newton was lucky to have followed Descartes and to have been able, as he might have said himself, to stand on Descartes's shoulders. I hope I have shown that Descartes was effectively responsible for single-handedly introducing the notion of laws of nature into natural philosophy. He did so, however, by drawing upon his background in mathematics. Moreover, realizing that he could not proceed without developing metaphysical foundations for his physics he turned, as Funkenstein and others have noted, to the providentialist theologies developed in the thirteenth and fourteenth centuries and turned them into a secular theology for his own purposes. To be sure, those purposes quickly went beyond what was required merely to underwrite his laws of nature, but this is where they found their original stimulus. Descartes's secular theology in turn was another important aspect of Descartes's influence: it is surely thanks to his lead that a number of the more devout, or philosophically thoughtful, among his near contemporaries also began to believe, in a way that natural philosophers had not previously, that "to treat of God from phenomena is certainly a part of natural philosophy."113 112 David Gregory, "Author's Preface," The Elements of Physical and Geometrical Astronomy (London, 1715), reprinted in Paolo Casini, "Newton: The Classical Scholia," History of Science 22 (1984), 1-58, 48-9. The Principia. Mathematical Principles of Natural Philosophy, a 113 Isaac Newton, new translation by I. B. Cohen and Anne Whitman (Berkeley, 1999), 943. I cannot resist observing that the thinkers in the Scientific Revolution who are taken to be in the first rank coincide with those who were most concerned with metaphysics and theology. Huygens and Hooke have never really been given their due, for example, but have been regarded as second-rank thinkers. The fact that Robert Boyle is regarded as a more significant thinker than Robert Hooke can have little to do with their achievements in science (since posterity would seem to favour Hooke in that regard), but must reflect scholarly interest in a thinker who not only performed experiments but also reflected on the nature of God and other metaphysical issues (including the status of laws of nature). But this is another paper.

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