BMCR 2007.10.03

Aristotle and the Science of Nature: Unity without Uniformity

, Aristotle and the science of nature : unity without uniformity. Cambridge: Cambridge University Press, 2005. 1 online resource (xvii, 139 pages). ISBN 0511132581. $75.00.

This short book extends the findings of Falcon’s (hereafter F.) earlier work Corpi e movimenti: il De Caelo di Aristotele e la sua fortuna nel mondo antico, (Naples 2001) by explicating Aristotle’s arguments in De Caelo and Meterology on the motion and composition of celestial bodies. According to Aristotle, since celestial bodies display natural circular motion and, since the elements of earth, air, fire, and water all associated with rectilinear motion, it must be the case that celestial bodies are composed of a “first element” and not ultimately reducible to, say, fire as Plato held. As F. shows, the thesis regarding the celestial simple body was very controversial in antiquity and few of Aristotle’s contemporaries and commentators were inclined toward the view that celestial and sublunary natures are discontinuous. The point of F.’s present work is to explore the implications that Aristotle’s unique views on celestial bodies have for his understanding of the science of nature. The book is tightly argued and situates Aristotle’s arguments in the historical tradition of commentary upon his work in a clear and highly sophisticated fashion. It assumes a relatively high degree of familiarity with Aristotle’s corpus, making it less suitable as an introduction to Aristotle’s philosophy of science at the undergraduate level. It should be of great interest to advanced undergraduates and others who are interested in a highly engaging and important account of Aristotle’s understanding of the science of nature.

Chapter 1 offers a close reading of the opening to the Meteorology for the purpose of investigating how Aristotle’s conception of celestial bodies can be used to delineate the structure, unity and boundaries of Aristotle’s science of nature. F. argues that while the investigation of animals and sublunary phenomena has a definite “unity, structure, specificity, and discreteness” (6) Aristotle does not hold that the study of sublunary phenomena is an investigation carried out independently: the study of animal natures and celestial substances is part of a larger inquiry in which the study of celestial substances must come before the study of sublunary natures. The investigation of nature, then, is structured in such a way that the study of the celestial world precedes the study of the sublunary world. But is it the case that only methodological considerations unite sublunary and celestial studies? F. illustrates the unity of Aristotle’s investigation of nature by claiming that he wants to make a “fresh start” (9) from Aristotle’s well-known dictum that “it takes a man to generate a man” (e.g., Phys. 193b8). F. points out that a slightly modified version of this slogan appears in the Physics: “it takes a man and the sun to generate a man” (194b13) (9). The relevant point here is that Aristotle has in mind a causal unity of a certain type (not the material sort since celestial material is distinct from earth, air, fire, and water) and not just methodological unity; the different aspects of natural investigation outlined in the Meteorology display an explanatory unity that is ultimately dependent on an underlying causal unity. Human reproduction is investigated by certain patterns of specific patterns of explanation, but as it is causally dependent upon celestial activity the direction of explanation must proceed from celestial to sublunary. Having explained the structure and unity of the investigation of nature for Aristotle the final sections of Chapter 1 turn to delineating the boundaries of this investigation with respect to the study of the soul. F. shows that while Aristotle may claim that the study of the soul is preliminary to the study of life it is not part of the study of nature.

Chapter 2 takes up the question of how to provide a conceptual framework for the notion of body. F. turns to the opening lines of De Caelo and its assertion that the science of nature deals with bodies and magnitudes. F. characterizes De Caelo as offering a conception of body that functions as a polemic against the theory of body developed by Plato in the Timaeus (306 a 23-26) (46). By Plato’s lights, the material principles of bodies are the triangular surfaces: one can distinguish between the material body Great Pyramid of Cheops ( soma) and the geometrical solid ( stereon). F. points out that the metaphor of nature as a book has its origin in the Timaeus, where Plato maintains that the elementary principles are analogous to the letters of which words, propositions, and finally the whole of nature is composed; the science of nature is about the element ( stoicheion) and so ultimately about the geometrical principles that govern natural processes. For Plato, then, any cosmologist who maintains that earth, air, fire, and water are the fundamental principles of everything is incorrect because the true principles are ultimately geometrical. Aristotle, by contrast, maintains that the material principles of natural bodies are themselves bodies and, according to F., intentionally maintains a minimal notion of body that “accepts the ambiguity of body between soma and stereon” (48). For Aristotle the ultimate material principles of the sublunary world are earth, air, fire, and water, and he uses the term stoicheion to refer to each as an element. He also uses the term stoicheion to refer to the celestial simple body and though this simple body does not enter into the combinations of earth, air, fire, and water found in the sublunary world, it does function as an element of the celestial realm. Two key points about Aristotle’s science of nature follow from his unique conception of body. First, Aristotle holds that Plato is committed to the view that “the ultimate magnitudes from which the world is constructed are indivisible magnitudes” (32) and this assertion makes Plato’s position in the Timaeus a form of atomism. Aristotle’s conception of body that is divisible in three dimensions functions as a conscious rejection of the type of atomism found in the Timaeus. Second, Aristotle is rejecting the Platonic idea that the universe is a living being. Plato’s conception of body leaves room for an internal principle that explains why the plurality of bodies can be understood as unified thing. Aristotle, however, in developing a concept of body that cannot be analyzed using a distinction like that between soma and stereon maintains that the cosmos cannot be understood as a single living being. The cosmos contains causal unity (“it takes a man and the sun to generate a man”), but the discontinuity between the celestial and sublunary realms does not allow a view of uniformity such that one could conceive of the cosmos as a living being or animal or intelligent.

Chapter 3 deals with Aristotle on motion. The student of nature must consider motion, and the regular but complex motion of celestial bodies falls under her purview. Aristotle’s theory of natural motion maintains that with respect to natural motion every simple body has its own natural motion and that there is only one motion per simple body. By noting that the four sublunary simple bodies all move in a rectilinear fashion and cannot, then, account for circular motion, Aristotle uses his theory of natural motion to introduce the thesis of the existence of a simple celestial body that performs naturally circular motion distinguishing himself from his predecessors and contemporaries who maintain that celestial bodies can be accounted for by, say, fiery stuff. For Aristotle, an element must be added to the traditional earth, air, fire, and water scheme to account for phenomena studied by the science of nature. But it is not the case that the circular motion that is naturally performed by celestial simple bodies is the same as the complex celestial motion naturally performed by the celestial bodies we observe moving around the earth. Aristotle maintains that an explanation proffered by the student of nature will require an appeal beyond the existence of a simple celestial body and its naturally simple circular motion. To adequately account for the complex but regular motion that we observe, an appeal needs to be made to a psychological cause—a soul with the capacity for desire and thought. For Aristotle, celestial bodies are intelligent beings acting of their own volition, and it is this voluntary aspect of them that explains their motion.

Chapter 4 deals with the limits of Aristotle’s science of nature, and F. shows that Aristotle is quite pessimistic about the study of celestial bodies, which are not just perceptually remote but, as shown in the previous chapter, conceptually remote as well: they possess natures (psychological and material) that cannot be reduced to sublunary natures. Again, the sublunary and celestial are discontinuous; the celestial is not simply a special department of the sublunary. F. argues that there exists no cosmic nature over and above particular sublunary and celestial natures. The Aristotelian slogan that nature does nothing in vain for F. is best understood as pertaining to particular natures. There is no universal principle of motion and rest in nature because celestial bodies follow principles of motion and rest that are not reducible to those that hold sway in the sublunary realm. The upshot is a picture of the natural world that is not a causally closed system and one that can render all natural phenomena intelligible only by the invocation of “a certain number of extra-natural principles” (89). This same sort of epistemic pessimism applies to Aristotle’s account of the soul in De Anima and the ability of its account to extend to celestial natures. Despite the fact that celestial bodies are souls of a certain type as intelligent beings engaged in voluntary motion, their seeming lack of phantasia seems to remove them from the ways in which De Anima analyzes motion, thinking, and desire. F.’s argument is that Aristotle is reluctant to extend the results of the De Anima to those souls inhabiting the celestial world. We have, then, unity that results from the sublunary and celestial forming a single totality (“it takes a man and the sun to generate a man”), but we have pronounced discontinuity in that the conceptual resources developed to explain the sublunary world cannot be adequately extended to fully account for those beings that populate the celestial world.

The Epilogue examines the accounts of the doxographers and commentators in understanding Aristotle’s notion of celestial simple bodies. F. shows that Aristotle never adopts any of the expressions used by commentators such as “fifth substance” or “fifth body” revealing that he is well aware of the fact that he has arrived a view of the natural world and the place of celestial bodies in that world that is unlike any of his predecessors or contemporaries.

F.’s arguments for why Aristotle held to a unique view of celestial bodies and the element of discontinuity they introduce into his understanding of the investigation of nature seem successful. F. demonstrates through the doxographical tradition and Aristotle’s own texts that this view was held intentionally by Aristotle and very likely held with an eye to larger philosophical issues such as the natural motion and the philosophical definition of body. F.’s arguments for delineating the boundaries of biological and psychological investigations seem successful as well. He shows clearly that while nature as a system does have causal links, the resources developed for investigating sublunary bodies and the ensouled entities encountered in the sublunary world cannot adequately explain celestial bodies.

It seems, though, that the epistemological picture could be clearer specifically with respect to the logic of scientific discovery in Aristotle on two points. First, F. states in Chapter 1 that, “it is fairly clear that the study of the celestial world comes before, rather than after the study of the sublunary world” (12). If we recall Aristotle’s distinction in Posterior Analytics I. 2 between “prior” and “better known” then celestial bodies are certainly prior and better known “in the order of being”, but in terms of the order of investigation celestial bodies, it would seem, must come after sublunary investigations. It seems that setting out clearly how we come to know about celestial bodies at all will have some bearing on the discussion at hand. As Aristotle points out in the Ethics we are to always ask whether we are on the way to or from first principles (1095a33). Second, the notion of how first principles function in the overall causal order has become somewhat diminished as F. has moved Aristotle further away from a “cosmic” conception of teleology and further toward the Democritean side of the teleological equation. F. states that “some grasp of the celestial world is not only necessary but also preliminary to the attainment of an understanding of important features of the sublunary world” (111). He insists on a qualification of “some grasp”, but the question becomes how do “first substances” interact causally with sublunary phenomena? If the sun is causally linked to man begetting man and if a gap of discontinuity exists between the celestial and the sublunary, then is the student of nature not cut out of a key slice of the causal picture?

The above criticisms are minor, and overall F. has offered up an extremely compelling set of tightly linked arguments showing that Aristotle’s position on the discontinuity between the sublunary and celestial worlds has wide ranging implications for the integration of sciences such as biology and meteorology and for how Aristotle understands the “system” of nature as a whole. F.’s arguments show how subtly Aristotle works his way between Plato and his notion of nature as intelligent thing with a strong (to say the least) cosmic teleology and atomists like Democritus who maintain that nature amounts to a mere plurality of bodies that operate with no teleological constraints. Bringing to light the implications of Aristotle’s “first substance” shows more clearly what this middle ground looks like.

This book will be of interest to those wishing to gain a greater understanding of how Aristotle’s philosophy of science is situated historically—as I have stated the historical context provided with respect to doxographers and ancient commentators is outstanding—and those interested in contemporary interpretation of Aristotle’s philosophy of science. The index is a bit thin, but the footnotes are extensive and filled with references to a good deal of recent work related to Aristotle’s conception of science. Readers familiar with Aristotle’s philosophy of science will find a set of issues that will cause them to re-think their perspective. To cite just one example, F.’s discussion of body and his argument for why Aristotle refuses to distinguish between soma and stereon unintentionally sheds light on why an account of the ontological status of Aristotle’s mathematical objects can be so difficult to work out. F.’s states in the Acknowledgements that the “enormous possibilities” of Aristotle’s text remain “largely unparalleled” (xiv); the present book admirably bears out this claim.