Entry 0242: Aquinas’ Five Ways and Aristotle (V)
Third Way, Leo Elders affirms that for
Aquinas the possibility of being and of not being belongs to things on account
of their matter. And more specifically regarding the influence of Aristotle,
Elders affirms that “The ‘it is impossible that these things always exist’ is a
principle given by Aristotle in the De
caelo 1 cc. 10-12 and accepted by St. Thomas who even explains it in a
subsequent line: ‘for that which can not-be, at some point is not.’ This
statement is the central point of the argument: a corruptible thing which would
never cease to exist, would have the possibility of not being corrupted, while
at the same time it is corruptible. But this is impossible. (See In I De caelo, 1.29, n.283 and 1.26,
Later Elders explains that regarding the influence of Aristotle on the Third Way, “some have pointed out to Metaph. XII 6, 1071 b 22-27 as the source of the argument: What is possible, does not have existence of itself but depends on something in act; of itself a possible being remains in potency; from the point of view of possibility alone at some time nothing is.” And then Elders adds that “More recently scholars have drawn attention to the De caelo I 12, where the statement is found: ‘What can not be, at a certain time is not.’ With this insight Aristotle provided an essential element for the argument as we find it in the Summa theologiae.” (2)
(1) Leo J. Elders, The Philosophical Theology of St. Thomas Aquinas, (Leiden, The Netherlands: E. J. Brill, 1990), 102-103.
(2) Ibid., 107.