Page - 172 - in The Priority of Locomotion in Aristotle’s Physics

more posterior it is in its coming to be. Accordingly, the farther away some- thing is from the end of this process, that is, the fewer the stages of develop- ment through which it has passed, the more prior it is in its coming to be. A definition of priority in coming to be then reads as follows: PRIORITY IN COMING TO BE: Of two things x and y, both individuals of kind k, x is prior to y in coming to be k, iff x is at a stage of the k-specific sequence of developmental stages through which y already passed. This means for example that in the process of becoming a man the stage of being a boy precedes the final stage of being a man and accordingly every man will have passed the stage of boyhood in his development before reach- ing full manhood. Therefore, the boy is prior in coming to be to the man, as the seed is to the human being. In looking at the definition of priority in essence in connection with prior- ity in coming to be, it now becomes clear why Aristotle comes to assert the reversed priority claim. As we have seen above, x is prior to y if x fulfils their common essence to a higher degree than y. Being prior in essence for things that are coming to be means being more complete. Thus, if x is prior in essence to y, x is at a stage of the k-specific order of development which y has not yet reached. In the opposite case, y is at a developmental stage which x has already passed. According to the definition just stated, y then is prior in coming to be to x and x is posterior to y while x is prior in essence to y and y posterior to x in this way. Thus, the relation of x being prior to y in essence is the converse of the relation of y being prior to x in coming to be k.14 Accordingly, there is no x for which it is true to say that it is prior to y in coming to be and also prior to y in essence at the same time and in the same respect. Hence, Aristotle is right to assert the truth of the reversed priority claim, i.e. the assumption that what is posterior in coming to be is prior in essence. 7.1.3 A different use of the term ‘locomotion’ The first of the two premises on which the argument for locomotion’s priority in essence is based, i.e. the reversed priority claim, has been estab- lished. The second premise is stated in sentence (3) of the passage quoted above and says that “locomotion belongs lastly to all things that are coming to be”.15 (1) If what is posterior in coming to be is prior in essence, and (2) if locomotion is, in the coming to be of living things, posterior to alteration 14 Or, if one would like to put it more formally: Pbeing(x,y) ↔ Pcoming-to-be(y,x). 15 τελευταῖον δὲ φορὰ πᾶσιν ὑπάρχει τοῖς ἐν γενέσει, Phys. VIII 7, 261a14–15: “But locomotion belongs lastly to all things that are coming to be.” 172 Locomotion is prior in essence ISBN Print: 9783525253069 — ISBN E-Book: 9783647253060 © 2014, Vandenhoeck & Ruprecht GmbH & Co. KG, Göttingen