アリストテレス「自然学」II9における目的と必然性

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I offer an interpretation, mainly on the basis of Physics II 9, of Aristotle's claim in his biological writings that explanation by necessity involving only material and efficient causes is consistent with an explanation of the same phenomena by purpose. My argument is directed towards the further question of whether Aristotle also believes that while the essences of certain biological phenomena are partly determined by their role in a teleological system, there is a complete account in terms of material and efficient causation of the conditions under which they exist. Physics II 9 presupposes his argument for the final cause as the nature in the primary sense in II 8, and is similar in theme to Parts of Animals 1 1 where Aristotle criticises the physiologoi on the ground that when they claimed that biological phenomena come into being by necessity, they fail to distinguish what kind of necessity is involved. At the beginning of II 9, Aristotle considers two alternative ways of understanding the necessity involved in generation ; either hypothetical necessity(HN) or HN plus simple necessity(SN). HN depends on a goal. If the goal is to be, it is necessary that certain other things come to be. SN, by contrast, depends on the nature of simple bodies and their movements. Aristotle locates the SN which the physiologoi take as the main cause of generation as a "necessary nature" (200a8) and regards this as explanatory of the goal, only insofar as the latter is purely materially specified as the matter of the goal(ω&b.sigmav; δι υλην). The goal taken as its matter is simply necessitated by its material components in the sense that the material components yield a specified condition for the existence of the goal. Thus Aristotle expresses two modes of necessity involved in generation as follows ; "The necessity, then, is on a hypothesis, but isn't necessary as the same way the goal(ω&b.sigmav; τελο&b.sigmav;) is necessary. For in the latter case the necessity lies in the matter, but in the former case the purpose lies in the λογο&b.sigmav; (account as design)." (200a13ff) Aristotle confirms the two modes of necessity in comparison with a mathematical reasoning. He compares both (1) "things which come to be based on nature(κατα <φυσιν)"(200a16) and (2) "things which come to be for something" (al9) with the necessity involved in a specific mathematical proof : given that the straight is thus and so, necessarily the triangle has angles whose sum is two right angles. While (1) is wider than (2) in terms of their extensions, they differ from each other in that the necessity involved in (1) is determined by the nature of underlying(υποκειμενομ), but the necessity involved in (2) is determined by goal. Aristotle defines nature in "κατα φυσιν" in (1) as a certain underlying based on simple bodies which have "natural tendency for change" (ορμη 192b18 cf. 95 al, 276a26) for both "substances" which "have a nature"(192b33) as formal or final cause and "their per se components" (cf. 73a34ff)which "do not have a nature" (193 a1) specified above as moving upwards belongs to fire. In that mathematical reasoning, the premises or components of the conclusion determine the necessity of the conclusion. This is said to be "in a parallel fashion" (200a16) with the case in (1). On the other hand, it is said to be "in a reversed fashion"(a19) with case in (2) in the sense that the goal which is achieved at the end of generation determines the necessity of the antecedent which comes no doubt earlier than the end. In this way, these two modes of necessity in generation are indirectly compared with each other via an example of mathematics. I conclude that while the purpose as design at the level of Adyoc determines what kind of matter should be employed in generation "as matter of λογο&b.sigmav; (200b8) , matter at the level of generation necessarily generates the matter of a goal by its own power, according to the program which is laid as design at the level of λογο&b.sigmav;. This allows us to say eg. eyeball and optic nerve etc. are an eye by themselves for the sake of seeing(cf. 1041a26). By distinguishing the level of λογο&b.sigmav; in which the purpose lies from the level of generation in which material necessity lies, Aristotle sets up the compatibility between teleological explanation of biological phenomena and explanation by material necessity in which both HN and SN lie.
日本西洋古典学会の論文
1994-03-28

著者

千葉恵
北海道大学文学研究科

アリストテレス「自然学」II9における目的と必然性

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