Nature, Change, and Agency in Aristotle's Physics

CHAPTER I. NATURE AS INNER PRINCIPLE OF CHANGE: The concept of "nature as inner principle of change" is fundamental to Aristotle's theory of the physical world; it is the object of the present thesis to substantiate this claim by tracing the effects of this idea in Aristotle's rejection of materialism, in his doctrine of "natural places", in his definition of change and process in general, and (via the latter) in his notion of agency in general and the supreme Unmoved Mover in particular. Aristotle elucidates "natural" by . contrast with "artificial", holding that natural substances not merely collectively but as individuals each possess an 'innate impulse of change'. But this must be explained so as to allow for the fact that no change is entirely independent of external conditions. If, however, change were totally dependent on external conditions, its occurrence would be inexplicable, and the very concept of "change" would be incoherent. This latter conclusion emerges from an examination of the ancient paradox of becoming and Aristotle's treatment of it. The paradox is expounded. Aristotle answers it by showing that language assumes a continuing subject of change. But this assumption meets the problem only if the metaphysical category of substance is also assumed, and along with it some distinction between substance-constitutive and non-substance-constitutive characteristics. The former mark off their subject as a thing of a certain causal type; thus change, in presupposing a substantial subject, presupposes one that makes some causal contribution to its own changes. But Aristotle means more than this by 'nature as inner principle'. He holds a natural substance to be (like a craftsman) the autonomous determinant of certain changes; these therefore (by contrast with changes not so determined) are "natural", as manifesting the substantial nature. This problematic notion is taken for granted by Aristotle in the Physics, but can be seen to rest on his metaphysic of substance. It is a consequence of this that the natural change of a given substance be of one kind and display a unitary pattern reflecting the unity of the substance. This view cripples scientific method as we understand it, but Aristotle's idea of substance anyway cuts him off from the approaches successfully operated in later mechanics and chemistry. A summary of the ground so far covered introduces a further sense in which Aristotle's natures are "inner" principles of change: the subject of change is not (as in artifice) external to the being which is the source of change. CHAPTER II. WHAT THINGS HAVE NATURES? Aristotle begins Physics II 1 with a list of organic and inorganic things 'manifestly' possessing "natures" in the sense explained. But our explanation has left open the question of the extension of this concept, and supplies as yet no theoretical justification for his choice of items on the list ((1)). Aristotle's inclusion of complex objects such as organisms raises a problem. Whatever has a "nature" is a substance, and a substance is a per se unity; but how can something complex and composed (as are organisms) of simpler substances be such a unity? Aristotle is entitled to count organic creatures as substances (and for him they are so par excellence) only if, as against the "materialists", he can show them to be more than mere arrangements of components. In Physics II. 1 he presents (without distinguishing) two materialist positions: one (i) identifies an object's "nature" with its proximate matter; the other (ii) asserts the simple bodies to be 'the whole of substance'. In II 1 he argues against (i) alone, with varying success. . But it is (ii) that poses the graver threat to his view of organisms as per se unities. This view, which Aristotle at no point abandons, connects closely with his doctrine of necessity and his teleology. But has it any firmer ground than a presumed analogy between nature and artifice? Aristotle's reasoned defence comes in Physics II 8, where he argues against Empedocles' version of the second materialist position as applied to organic structure and development. Aristotle's argument has apparent flaws, but is effective in the context of the view that the simple bodies are substances that express their natures through locomotion in diverse directions. On this premiss, neither mechanical nor chemical combination could account for organic phenomena. Hence Aristotle has a rational basis (a) for regarding organisms as per se unities endowed with substantial "natures", and (b) for his teleology. Despite their close connection, (a) and (b) are not to be equated. Aristotle's theory of organic substance is (pace A. Gotthelf) fundamentally metaphysical. CHAPTER III. THE DEFINITION OF CHANGE In Physics III 1 ff. Aristotle undertakes to elucidate 'change'('peragoAr)') and 'process' ( 'xgvwus'). Although the terms are not synonymous he treats them here as interchangeable, i.e. as if all change were process. This tacit restriction of the meaning of 'change' is due (it is argued in this chapter) to his preoccupation with "natural" change, although "nature'! (as he himself makes clear) is only one type of source of change. Under the general concept change we may distinguish (a) that of the "emergence" of some new property and (b) that of "process", which includes conditions leading up to an "emergence". The concept here sketched of "process" leaves open the question of mathematical continuity; it also allows a subject to be regarded as- 'in process' on account of imminent causal activity in some other subject. This entails that there is no contradiction in predicating (as Aristotle occasionally does) the term 'process' of a subject which passes all at once from an old to a new state. Many phenomena can be described either as emergences or as processes, although locomotion has to be regarded as process. But in Physics III Aristotle assumes that all change-phenomena are to be approached via the concept of "process". This is because he cannot otherwise preserve the metaphysical connection between "change" and "natural substance". This is easily shown for organisms. The simple inanimate bodies can be accommodated to his scheme by supposing an absolute difference between "upwards" and "downwards" (i.e. the doctrine of "natural places). Change, on this view, is necessarily directed to a terminus; thus it may be regarded as "incomplete", which for Aristotle is what fundamentally distinguishes it from conditions of non-change. This "self-terminating" character of Aristotelian change is what makes it especially puzzling, more, so than Plato's "becoming". We now consider in detail the account of Ill 1 ff.) Since change or Hivnobg expresses substance, it too must be real and actual; hence not only must every characteristic changed from and to fall into some definite category, but so must change itself. Aristotle puts it into the category of "Relation" for want of a better, thereby committing himself to the view that all change involves an agent-patient relationship. Although obscure, the formal definition of MtvriObg in III 1 is not circular; this is clear once its reference to 'potentiality' is correctly interpreted. It permits adequate distinctions between actual change, the actual subject, and the actual condition in which a change terminates. It entails a fundamental type difference between change and non-change, and shows why earlier thinkers were so mystified by this topic. Aristotle's own doctrine of substance and the Categories turns out to depend on his conception of change as self-terminating. The III 1 definition can be interpreted in two ways; according to one of these the subject need not undergo perceptible transition. But this definition covers only natural and purposed change or xtvnotg. However, in Physics VI Aristotle attempts another account (not that he ever appears to renounce that of Physics III); the metaphysic of nature and substance is now in abeyance and the central concept is the inclusion, by any one change, of infinitely many temporally (and in some cases spatially) smaller changes. Change is now distinguished from non-change in a way requiring the former to be temporally intermediate between its termini (which was not necessary on the account of Book III). But qualitative change is made to fit this scheme only by a bad argument, whose force Aristotle himself refuses to acknowledge in another context. Still worse problems are generated by his continuing assumption that change is directed to a terminus. The attempt to combine this with the analysis in terms of mathematical continuity produces paradoxes, as Aristotle realised when he came to work out the .cosmology of Physics VIII. Thus in VIII 8 he argues against the Book VI view that a change consists of infinitely many shorter changes, and there he also abandons the associated view that change necessarily occupies a period of time between its termini. CHAPTER IV. AGENT AND PATIENT In the Physics the notion of "agent"/"patient" (xbvouv/xbvodpevov, "changer"/"changed") is more closely linked than any other to the concept of change. In III 3 Aristotle reformulates his definition of the latter in terms of agent and patient. His grounds are obscure, like much else in his treatment of agency. But clearly he holds that (i) for every change (xb'vnobg) there is a changer OtvoOv); (ii) the changer is distinct from the changed (or subject of change); (iii) to act as a changer is not to change (intransitive). The first position may have seemed plausible because 'xuvebv' has to be put in the grammatical passive to express intransitive change. Thus rules of grammar prescribe that for every xbvpobg there is a xtvoupcvov; but this alone does not validate an inference from 'xbvqobg’ to 'xuvoOv'. In III, Aristotle identifies the "changer" as that which confers the form typifying the change. But in natural change the substance whose nature dictates the form is also the sub

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