THE MODERN MISUNDERSTANDING OF ARISTOTLE'S THEORY OF MOTION

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SUMMARY. In the Physics, Aristotle defines motion as 'the actuality of what is potentially, qua potential' (Phys. 201b5). This definition has been interpreted countless times and has been the subject of heated controvery. At issue today is whether ~,re)t~XeLa refers to motions as a process or a state. Accordingly, if the idea of ~vre)t~Xe~a is believed to refer to a process, it is translated to mean actualization. If on the other hand it is taken to refer to a state, it is translated as meaning actuality. In the first instance, known as the 'state-view', a change is defined as being the state of a changing object when it is actually potentially F, for some F ~. In the second, or ~process-view', a change is defined as the actuaBzation of a potentially. 2 It seems to me that both views mistakenly assume that Aristotle succeeded in defining motion as motion. As a consequence, the discussion has focused on a presumed content that the definition does not offer. Indeed, were it the case that Aristotle's definition was adequate, there would hardly be any point in even considering the question of whether he had intended to regard motion as being a state or a process. In this paper I examine both of these views and offer an alternative interpretation of my own that differs markedly from either. Additionally, I shall show that just as Aristotle's definition represents a projection of his particular attitude toward nature - so also recent interpretations of his definition represent a projection of the attitudes of modern thinker's toward Aristotle's philosophy.

Key words: motion, actuality-potentiality, form-matter, praxis-poesis, process-result. THE CONCEPT OF MOTION

A r i s t o t l e defines m o t i o n as ' t h e a c t u a l i t y o f w h a t is p o t e n t i a l l y , q u a p o t e n t i a l ' (Phys. 201b5) o r as ' t h e a c t u a l i t y o f w h a t is p o t e n t i a l l y , as s u c h ' (// r o t ~VV~eL 6vros" ~ ' r e ) k ~ X e t a , r/ roLovro~) (Phys. 2 0 1 a l l ) . 3 T h e m a i n p o i n t at issue in t h e m o d e r n c o n t r o v e r y is a b o u t h o w t o u n d e r s t a n d t h e i d e a of potentiality. A c c o r d i n g t o t h e process-view, w h e n s o m e t h i n g is p o t e n t i a l it is a c t u a l l y t h a t at a g i v e n m o m e n t - f o r e x a m p l e , t h e p r o c e s s b y w h i c h t h e b u i l d a b l e b e c o m e s b u i l d a b l e . T h e final p r o d u c t is a c c o r d i n g to this v i e w t o t a l l y i r r e l e v a n t to t h e d e f i n i t i o n o f c h a n g e o r m o t i o n . I f this w e r e so, t h e n A r i s t o t l e w o u l d h a v e r e f e r r e d to, say, t h e m a t e r i a l s o u t o f w h i c h a b u i l d i n g was b u i l t as t h e a c t u a l i t y o f b r i c k s a n d s t o n e s q u a b r i c k s a n d s t o n e s ; o r as t h e p r o c e s s o f b e i n g b r i c k s a n d s t o n e s as s u c h , i r r e s p e c t i v e o f t h e i r p u r p o s e . C h a n g e w o u l d t h e r e f o r e b e t h e p r o c e s s o f this p r o c e s s o f b e i n g b r i c k s a n d s t o n e s as such. It w o u l d t h e r e f o r e be a c a s e o f d e f i n i n g t h e b u i l d a b l e q u a b u i l d a b t e - or, as K o s m a n p u t s it, o f d e f i n i n g ' t h e p r o c e s s b y w h i c h t h e b u i l d a b l e b e c o m e s buildable, r a t h e r t h a n , as A r i s t o t l e h a s in m i n d , b u i l d i n g , t h a t is, t h e p r o c e s s b y w h i c h t h e b u i l d a b l e b e c o m e s b u i l t 2 B u t t h e n t h e

Journalfor GeneralPhilosophy of Science 26: 1-10, 1995. © 1995 Kluwer Academic Publishers. Printed in the Netherlands.

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aetual-potential distinction would lose its meaning. Change would be, as it were, the process of this process of being bricks and stones. That is to say, motion would be absurdly defined as the motion of motion - in which case potentiality would not be defined in terms of actuality, and this would run counter to Aristotle's definition of these terms. Aristotle explicitly suggests that potentiality per se cannot exist (cf. Phys. 201 b 33202 a 1). The state-view shares assumptions that are similar to these of the processview. Change is defined as the state of the changing object when it is actually potentially F, for some F. Therefore being 'only potentially F ' (which is different from being 'actually potentially' F), means being potentially potentially F. But this results in a confusion of terms. Actuality and potentiality are technical concepts developed by Aristotle for the express purpose of distinguishing between what is in motion and what is not, between the incomplete and the complete - where motion betokens incompleteness. According to this interpretation, it would appear that Aristotle defined motion as the completion of the incomplete. However Aristotle explicitly rejects this possibility when he denies that motion is an absolute and simple actuality (cf. Phys. 201b 25-30). Both of these interpretations assume that Aristotle was indeed capable of arriving at a definition of motion as such, when in fact no such account could have been given by him. Formulated in the most extreme terms, both views end in absurdity. If motion is taken to be a process, then we are confronted by a circularity of definition. What is being asserted is that change is change; and motion is thereby defined as the actuality of what is potentially motion qua potential motion. As Kosman has rightly observed, 'to say that motion is the process of actualization by which a potentiality is actualized is to attempt to define motion in terms of the very concept in question, that of the process of actualization'. 5 On the other hand, if motion is regarded as a state, the implication is that change is defined by what does not change, or that motion is no-motion but rest - which is manifestly a contradiction. Thus the controversy over whether ~urek~X eLa means a process or a result boils down to this: in avoiding entanglement in a tautology, one is trapped in a contradiction. And in avoiding the entanglement of contradiction, one is entangled in either a tautology or circularity of argument. Modern advocates of the process-view and of the state-view agree in that 'potential' is the equivalent of 'change-as-such'. This is however not the case. Indeed, according to Aristotle, there is no change-as-such; rather change is toward something else that is in itself unchangeable. For Aristotle, potential is the equivalent only of change, and neither has meaning in itself, but only concerning some end. The frame of reference for giving an account of motion is always the unchangeable final product. According to Aristotle, potentiality is the process that something is in when it has not yet assumed its final form - for example, the process by

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which the buildable becomes built. In this instance, potentiality refers to a house whose construction is yet incomplete. The point is that potentiality per se, without its end being taken into account, is as incomprehensible as would be the process of building without taking into account what is being built. To understand Aristotle's theory of motion, we have to begin by considering the assumption that underlies the theory. The first question is whether motion is definable for itself or concerning something else. There is any sense in determining whether motion is a process or a state, only if motion is definable for itself. However, Aristotle maintains that motion is definable only concerning something else other than itself - or more specifically, in relation with its opposite, which is rest. And since Aristotle cannot offer an immanent definition of motion, the whole issue of whether motion is a process or a state - and therefore the very controversy a m o n g modern interpreters - is irrelevant to his definition. Aristotle offers only a paradoxical definition of motion. This is not to say that he denies its existence. This would have been the position of the Eleatic school, which Aristotle criticized. Aristotle recognizes that motion exists, but regards it as impossible, or at least difficult, to be grasped. 6 The epistemological difficulty lies in the very idea of potentiality. According to Aristotle, something cannot exist qua potential, or potentially in itself. In this, potentiality is like matter. Matter can exist only if it is actual or, what amounts to the same thing, if it possesses a form. And since motion as such must be defined in terms of potentiality as such, it cannot be defined within the framework of Aristotle's system of thinking. Indeed the same problem arises concerning the definition of matter as in the case of motion. F o r m precedes matter - which is to say that matter is explained by means of form. Matter qua matter exists neither ontologically (Metaph. 1029) nor epistemologically (Metaph. 1036). Matter is precisely that which does not change; in other words, matter is that which does not exist in itself. Existence is that in which change is given - namely, form (Metaph. 1070-1). Thus Aristotle cannot define motion as either a process or a state since he gives no consideration to change as such. Change is the transition of matter from one form to another, and this can be grasped only as a transition from the potential to the actual. But transition per se is undefinable. F o r to attempt to define it is like trying to define matter without form; and this is obviously beyond the scope of Aristotle's philosophy. Aristotle offers no principle of change-in-itself. He is only capable of considering f o r m as either final form or transitional form (that is, the transition from one form to another), which is an alternative possibility that neither the process-view nor the state-view takes into account. Stated in the most general terms, actuality precedes potentiality, in that potentiality is explained by means of actuality (Metaph. 1049-50). Rest (that is, the end) therefore precedes motion, and the former explains the latter. 7 Hence the only definition of motion offered by Aristotle, taking

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into account the whole corpus of his writings, is paradoxical. Let us consider alteration as an instance of motion (cf. Phys. 225 b 10226 b 17). What is motion (Kiu~To~9)in the sense of alteration (&XXo~o~aLg)?8 Change means that a being becomes another being. But if this other being were not already present in the original being, we could not properly speak of an alteration having occurred. We could only know that one being has succeeded another. Thus alteration means that the new being was already included in the former being. Change is therefore something impossible to grasp, because here it is asserted that being is within itself different from itself. Hence the transition in which one being becomes another takes place within the original being. To state the matter in a Hegelian style, the transition of being to non-being takes place within being itself. Now, if being and non-being are respectively called 'actuality' and 'potentiality', it follows that motion must be regarded as "the actuality of what is potentially, qua potential" (Phys. 201b5). Thus Aristotle, who resolves the contradiction of non-being in being by invoking the opposition between the actual and the potential, is ultimately compelled to conclude that motion is indeed an actuality - albeit an actuality that is incomplete. 9 What exists potentially must be actually potential. Aristotle is constrained to join two opposite terms here, so that he is forced into a contradiction. Otherwise it would be nonsensical to refer to a potentiality. Moreover he is plainly aware of the difficulty, since actuality means completion and potentiality means incompletion. The interpreters of Aristotle fail to see that the difficulty is inherent in the very Aristotelian idea of motion. So, for example, Terry Penner 1° maintains that the problem is merely one of ambiguity in the relation between process and product, and that it ultimately derives from the ambiguity of language. In my view, however, the root of the problem lies in Aristotle's assertion of an actuality that is its opposite a potential actuality or an actual potentiality. This idea works against the very distinction between the potential and the actual that he had laid down to define motion as something potential and not actual. Indeed, Aristotle sometimes defines motion as "the actuality of what is incomplete" (De Anima 431 a 6) and sometimes as "an incomplete fulfillment of the movable". 11 The ambiguity of language is not fortuitous, but is rather grounded in Aristotle's problematic attempt to come to grips with the selfcontradictory idea of potential actuality and actual potentiality. Aristotle becomes particularly difficult to follow when he undertakes to define motion in detail. It is then that he confronts the limitations of his own thought. 12 Thus the ambiguity of the relationship between process and product to which Penner refers lies in the very idea of motion. Motion, or rather the process of motion, has meaning only regarding its product or result. Infinite motion is thus impossible because it has no rEXog. For Aristotle, an end product is something easier to understand since it is not in motion. Whatever lacks motion is not understandable by means of motion, whereas that which is in motion is understandable only by means of its rehog. -

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Motion is therefore grasped through its opposite. Aristotle is undoubtedly conscious of the difficulty implied here, as is evident when he contends in this regard that "it is hard to grasp what motion is" (Phys. 201 b 33). Motion has to be characterized as a deficiency - as a potentiality without actuality; so that, like matter without form, it is beyond comprehension. Motion is therefore not definable in its own right, so that there is no definition of motion proper. Motion is not definable in terms of itself, but only by means of its limits - by its terminus ad quo and terminus ad quem; by what precedes it and comes after it. i3 THE ORIGIN OF THE CONCEPT OF MOTION Like all the Aristotelian ontology, Aristotle's ontology of motion originates in the model of human activity. However he is unaware of this. Indeed, he even inverts the relationship. So, for example, he contends that art is an imitation of nature, since it consists in bestowing form on the matter. 14 Yet Aristotle conceives nature as oriented toward a goal (Phys. t99). Aristotle regards nature as imitating human art. Thus his theory of nature is a construct derived from human activity. According to the principles of the form-matter and actuality-potentiality distinctions, Aristotle distinguishes between production on the one hand, and consumption and use on the other. Aristotle is unaware that he has reversed the order of these distinctions. He is also unaware that his distinctions between form and matter, and between actuality and potentiality, are an inversion of his basic model. Basically, he distinguishes between human production and consumption (or use), where matter is the object of ~'obTm~, and form is the object of zrpa~L~. Therefore, to understand Aristotle's conception of nature in general, and of motion in particular, it is necessary to analyze his conception of men and society. Aristotle distinguishes between two kinds of human activity: zrpa~t9 and rcobTa~9 (Metaph. 1048b). The first is not motion, and the second is motion (Eth. Nich. l140b). In Metaphysics 1048b, a key passage for understanding the problem of motion, Aristotle contends that while all motion is incomplete, actuality is always complete. Completeness and incompleteness have to do with whether the reXo~ is in the activity itself or in its end; in the latter case, motion is subordinated to the end. An activity that is in itself a reho~ is called by Aristotle rrpa~t~. In this passage, the completeness of rrpa~L¢ is set in opposition to motion. For this reason, zro~Tm~ is ethically inferior to 7 r p a ~ . I I p a g ~ is the model of moral behavior, since in ethics, "doing well is in itself the end" (Eth. Nich. 1140b7). It should be noted that the completeness of 7rpa(t¢ does not mean quietude of being. Quietude of being is rather the correlative of uncompleted motion, 15 which attains completion only when it ceases. Thus quietude of being is already to have acquired learning, rather than learning itself; or to have arrived at a place, rather than traveling to it.

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IIpa~t~ refers to the end of the activity, and zro{~lo~ refers to the means. Thus the zrpa~L~-rro{rlm~ distinction overlaps the distinction between ends and means. IIpag~9 is the form of the activity of the consumption and use of things that are neither made for consumption nor serve as a means to an end other than themselves. Thus Aristotle cites the example of a bed as a means of 7rOa£~ (Pol. 1254a). On the other hand, productive use requires instruments that are different in kind from those employed in consumption. These instruments are means to an end other than their use - say a shuttle (PoL 1254a). The distinction between rrpa~L~ and 7ro~/cr~ is so sharp, that different classes of individuals characteristically function in one or other of these two activities. Masters, by their very nature, function as consumers, namely, as subjects of zroa£L~ while slaves are characteristically producers, that is, subjects of rro[~/o~. The latter have no independent existence, they exist only to execute the master's orders, that is, to achieve his ends. 16 Slaves, as subjects of 7ro{~Tm~, that is, as consumers, do not participate in the activity of consumption. ]7 Masters on the contrary, as subjects of 7rpa~t~ and, consequently, as consumers, do not participate in the activity of p r o d u c t i o n J 8 Even when they appear to be doing so, by imparting orders to the slaves, they are still acting within the f r a m e w o r k of rrpaf~. They are merely using their slaves, and using is a m a r k of rcpa~L~, not of 7ro~r/o~. This strange assertion becomes comprehensible within the framework of Aristotle's intention to distinguish sharply between motion and perfection, 7ro{r/a~9 and zrp0~Lg, potentiality and actuality. The polar distinction between master and slave is essential for the clear distinction of his own categories. Without it, the relational ideas of rro~at9 and rcpa~Lg, potentiality and actuality, motion and perfection, would become merely relative and, therefore, problematic. Aristotle is trying precisely to avoid this relativization of his categories. His definition of motion as such (that is, of potential qua potential) leads just to such a relativization of the relational ideas of actual and potential. Aristotle therefore does the very things he sought to avoid. To maintain his sharp distinction between master and slave, Aristotle further distinguishes between two kinds of instruments: instruments of trOffer9 and instruments of rroi~a~£. Aristotle consider slaves as instruments of zrpa(~9 and not of rco{rlm~, since the master's acts in relation with his slave are acts of rcpa~9. It is the instruments of the slaves that are instruments of 7roir/o~9, that is, their activity is productive. Aristotle states: Instruments are of various sorts. Some instruments are living, others lifeless. In the rudder, the pilot of a ship has a lifeless, in the lookout man, a living instrument; for in the arts the servant is a kind of instrument. Thus, too, a possession is an instrument for maintaining life. So, in the arrangement of the family, a slave is a living possession, and property a number of such instruments; and the servant is himself an instrument for instruments. For if every instrument could accomplish its own work, obeying or anticipating the will of others, like the statues of Daedalus ... if the shuttle would weave and the plectrum touch the lyre,

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chief workman would not want servants, nor masters slaves. Now the instruments commonly so called are instruments of production whilst a possession is an instrument of action (rroa(t~). From a shuttle we get something else besides the use of it, whereas of a garment or of a bed there is only the use. Further, as production and action are different in kind, and both require instruments, the instruments which they employ must likewise differ in kind. But life is action (rroe~t~) and not production (rrobTat~),and therefore the slave is the minister of action ... The master is only the master of the slave; he does not belong to him, whereas the slave is not only the slave of his master, but whollybelongs to him (Pol. 1253b28-1254a14) From the point of view of my thesis, the point of interest in the above quotation is that the slave functions, in relation with his master, as a process or motion. Whereas the master represents the end that imparts purpose and meaning to the existence of the slave. As in the case of motion, here too, 'complete' is that who serves its end (the master) or that who achieves his end. 'Incomplete' is the slave, who is not defined in himself but only in relation with his master. 'Incomplete' also is that which has not yet achieved its end, that which is still in the process of production. It becomes complete or perfect when the process is completed and the object becomes available for consumption or non-productive use. This sharp distinction between r c p a ~ and woi~Tm~ is the basis for the distinction, in Aristotle's general interpretation of nature, between natural process and result. Nature is not taken to be a natural process as such. Nature is grasped by virtue of its fruits: you understand a seed by understanding the mature plant into which it should develop, as you understand production by virtue of the product (cf. Phys. 199). Nature is therefore grasped by the idea of zrolrlatg, that is an idea subordinate to the idea of rrpa(~9. Like human beings, nature also uses means to achieve ends. However, the fruit or product of nature, as of human activity, is distinct from the process of production (that is, motion). This view of motion as dependent on ends has not only theoretical but also practical significance. Aristotle based his philosophy upon the general assumption of his time, that men do not generate motion but they merely make use of it. Motion, according to Aristotle's basic assumptions, is not consciously generated. Motion is not definable as such. It is what lies between a state where it has not yet come into operation and the state where it has already ceased to operate. Therefore the question raised by the commentators (that is, whether motion, for Aristotle, is a process or a state in itself) ignores this fundamental aspect of Aristotle's philosophy. Their question is motivated by modern physics rather than by Aristotelian assumptions. Contrary to modern technology, the Greeks did not create natural motion. The Greeks grasped natural motion only in use; it was therefore cognizable not as such but only as goal-oriented. Aristotelian physics (that is, nature) is ultimately analogous to art and production that, like motion, are goal-oriented. Therefore, motion cannot be regarded either as a process or as a state in itself. For the assertion of motion as a process, Aristotle would have to

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acknowledge the generation of motion, and to define motion as such. But he defines it only in relation with its result. Therefore, motion is a potential result and only as such it can be grasped. For the assertion of motion as a state, Aristotle would have defined motion not as such but in terms of its result. Modern physics bases its opposition to Aristotle's theory of motion on artificial, produced motion. Modern physics explains the production of motion by means of natural laws, since natural laws are the conceptual expression of the mode of motion itself. The knowledge we need to produce motion is not about motion but about the mode of motion. The modern misunderstanding of Aristotle's approach derives, I believe, from the application of modern patterns of thoughts to ancient categories. The process view of Aristotle's interpreters is plausible only if motion is grasped in itself and not through rest. This is precisely what modern physics has attempted to do, but not so Aristotle. We may therefore assert that the process-view interpreters are trying to interpret Aristotle's idea of change through the categories of modern physics. Modern physics, unlike Aristotle, cannot understand rest as such, and therefore defines it in terms of motion: as an equilibrium of forces. Aristotle, on the other hand, defines motion in terms of rest. We must therefore try to understand Aristotle's approach not through, but in opposition to modern physics. Whereas modern physics regards motion as the primary state of things, Aristotle regards rest as the primary state of things. Motion he regards as a secondary state and, as such, he seeks to explain it. Aristotle asks what motion is, but explains it only indirectly as a transitory stage whose end is a state of rest. Modern physics, on the other hand, explains motion directly and not in terms of rest. So that, just as modern physics cannot understand rest qua rest, Aristotle cannot understand motion qua motion. 19 The new idea of motion developed by modern physics superseded the classical Aristotelian idea of being. The classical idea of rest was correlative to the idea of being. Being, in the sense of being-at-rest, was the end by which motion was explained. Therefore the idea of motion for the classicists was closely related to the idea of place, since to be at rest means to be at a certain place. For Aristotle, things are in motion when they are not in their natural place. Hence, when they reach their natural place, motion ceases. However, modern physics (after Kepler's assertion that place is a creation of the mind "omnis locatio mentis est opus ''2° denies the existence of a natural place for things. It has shifted the explanation of physical reality from place to change of place. 21 This shift of the explanatory criterion is a shift from explanation in terms of substance to explanation in terms of functions or in terms of laws. The idea of law has superseded the Aristotelian idea of Reality. For Aristotle, motion is a state of imperfection. For modern physics, motion is the natural state of things. Modern physics does not explain motion by some other state (in this case, rest). According to Aristotle, KWTIOL~can only be grasped through a Teko~ that is not itself

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m o t i o n , w h e r e a s m o d e r n p h y s i c s d o e s n o t n e e d a reX09 to e x p l a i n m o t i o n . G a l i l e i g o e s so far as to a s s e r t t h a t w h a t is at rest d o e s n o t e v e n exist. 22 S i m i l a r l y , N e w t o n , in his F i r s t L a w o f M o t i o n , refers to t h e c o n s e r v a t i o n o f m o t i o n . T h i s m o d e r n a p p r o a c h c a n n o t b e g r a s p e d in t e r m s o f t h e A r i s t o t e l i a n m o t i o n - r e s t c o r r e l a t i o n . M o t i o n is n o t d e f i n a b l e b y its e n d ? 3 K e p l e r , t o o , refers to a p e r p e t u a l , e t e r n a l m o t i o n , o n e t h a t d o e s n o t h a v e rest as its end. 24 K e p l e r e x p l a i n s his o w n a p p r o a c h as a n a t t a c k o n the A r i s t o t e l i a n i d e a o f final cause. F o r A r i s t o t l e , o n t h e o t h e r h a n d , e f f e c t i v e c a u s e ( m o t i o n ) is s u b o r d i n a t e t o final c a u s e (rest). T h e d i s t i n c t i o n b e t w e e n m o t i o n a n d its e n d p e r v a d e s all his p h i l o s o p h y a n d gives it its p a r t i c u l a r c h a r a c t e r . L i k e m o t i o n , m a t t e r is s u b o r d i n a t e d to a n d d e f i n e d b y f o r m ; rrobTm~ is s u b o r d i n a t e to 7 r p a ( ~ ; s e r v a n t to m a s t e r ; p o t e n t i a l i t y to a c t u a l i t y ; m e a n s to ends. T h i s d i s t i n c t i o n is b a s e d u p o n t h e p r i m a c y o f t h e r e s u l t o v e r t h e p r o c e s s , in t h e sense t h a t the r e s u l t e x p l a i n s t h e p r o c e s s , w h i c h is a p p r e h e n s i b l e o n l y in t e r m s o f its end. NOTES AND REFERENCES 1 The state-view is sustained in different versions and issues by: L. A. Kosman: 1969, 'Aristotle's Definition of Motion', Phronesis 14, 40-62; Jaakko Hintikka: 1977, 'Aristotle on Modality and Determinism', Acta Philosophia Fennica XXIX, 58-77; Mary Louise Gill: 1880, 'Aristotle's Theory of Causal Actions in Phys. III 3', Pronesis XXV, 129-147. In the state-view, motion is not defined in itself but defines a thing in a state of changing. 2 The process-view is sustained by Terry Penner: 1970, 'Verbs and the Identity of Actions', in Oscar P. Wood and George Pitcher (Eds.), Ryle: A Collection of Critical Essays, Garden City: Anchor Books, pp. 393-460. W. D. Ross: 1936, Aristotle's Physics, Oxford, p. 537. Edward Zeller: 1921, Philosophie der Griechen, Leipzig, II, 2, 351. James Kostman: 1987, 'Aristotle's Definition of Change', History of Philosophy Quarterly IV, 3-16. 3 Cf. also Phys. 202a6, 251a9, Metaph. 1065b16, 1065b23. 4 Kosman, op. cit. p. 43. 5 Kosman, 'Aristotle's Definition of Motion', p. 41. 6 The knowledge of motion has a philosophical evolution. At the beginning, motion was presupposed, and therefore it was not something explainable. Afterwards, with the Eleatic school, motion becomes an object of analysis although denied its existence. Plato recognized it as an illusion. Aristotle went forward, recognized its existence and, instead of deny it, considered motion as difficult to be grasped. 7 For a good account of the idea of change (motion) as different from the idea of activity, see Mary Louise Gill: 1880, 'Aristotle's Theory of Causal Action in Physics III 3', Phronesis XXV, 129-147. 8 This analysis of motion is inspired in Jos6 Ortega y Gasset's Preface to the Spanish translation of Emile Br6hier's Histoire de la Philosophie, Buenos Aires: Sudamericana, 1942, pp. 42-47. 9 Cf. Phys. 201 b, 257b9, Metaph. 1048b29, 1066a20. ~0 T. Penner: 1970, 'Verbs and the identity of actions - a philosophical exercise in the interpretation of Aristotle', in O. P. Wood and G. Pitcher (Eds.), Ryle, Macmillan, pp. 430 ff. 11 Phys. 257 b 8. Cf. Penner, op. cit., 433. ~2 L. A. Kosman gives a good insight about the impossibility of defining motion: 'For motion is the actuality of a potentiality which is aimed ultimately at an actuality other than the motion and fatal to it. Motion does not, therefore, just happen to cease, its essential activity

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is devoted to ceasing. Its being is auto-subversive, for its whole purpose and project is one of self-annihilation'. Kosman: 'Aristotle's Definition of Motion', p. 57. t3 In De Anima, it seems that Aristotle takes another approach. There he distinguishes between two opposite ideas of actualization: (a) actualization as the destruction of potentiality, and (b) actualization as its conservation. That is to say, there is a negative meaning (destruction of potentiality), and a positive meaning (its conservation) of actualization. Thought, for instance, is not a change, since change implies destruction (cf. De Anima 417b); it is rather conservation, 'progress toward itself' or 'on itself' as an inner return to actuality. But Aristotle adds 'towards its end', and therefore he does not change his basic approach, that is, the reference to the end. ~4 Cf. PA. 639b. Nature aims at the best and noble P.A. 645 a 25,670 b 24; nature is rational (G.A. 731 a 24, 744 b 15). Cf. also G.A. 760 b 26. Compared with art: GA 734b 20 735a 1,762a15, 775a20. With an artisan: G.A. 731 a 20, 730 b 15, 743a 25. Nature does nothing in vain: PA. 658 a 9, DC2. 15 In Aristotelian language it is redundant to speak about imperfect motion, since motion means already lack of perfection; notwithstanding, I use this expression to facilitate the exposition of the subject. ~6 ,... Some men are by nature free, and others slaves, and that for these latter slavery is both expedient and right' (Pol. 1255al). English translations are from Jonathan Barnes (Ed.): 1984, The Complete Works of Aristotle, Princeton. 17 'The best form of state will not admit them [the artisans] to citizenship; but if they are admitted, then our definition of the excellence of a citizen will not apply to every citizen, nor to every free man as such, but only to those who are freed from necessary services' (Pol. 1278a 5-13). 18 ,... the citizens must not lead the life of artisans or tradesmen, for such a life is ignoble and inimical to excellence. Neither must they be farmers, since leisure is necessary both for the development of excellence and the performance of political duties' (PoL 1328b37-1329al). ~9 Michael Boylan missed this point by asserting that the logic of modern science, especially that of biology, is similar to Aristotle's logic. Boylan fails to see the difference between the Aristotelian question concerning the what (the end) and that of modern Science concerning the how (the process). Cf. Michael Boylan: 1984, 'The Place of Nature in Aristotle's Teleology', Apeiron XVIII, June. 20 Johann Kepler, Opera Omnia, V. II, 55. 2~ See Ernst Cassirer: 1923, Einstein's Theory of Relativity, Chicago, The Open Court Press, p. 362. 22 Galileo Galilei, Dialogo, Berkeley, 1953, p. 58. 23 Sir Isaac Newton, Philosophiae Naturalis Principia Mathematica (1687), Berkeley 1947, p. 13. 24 See De Anima 417b5. J. Kepler, Gesammelte Werke, V. VII, Book IV, part. 3, p. 330. Dept. of Philosophy, University of Haifa, Mount Carmel, Haifa 31999, Israel.