Published online by Cambridge University Press: 05 May 2010
In the present paper I propose to examine St. Thomas Aquinas' third way of proving the existence of a God (henceforth TW), keeping in view and applying the proposals I have made elsewhere concerning the number andorder of the “Five Ways” and the role therein played by TW. I maintain that the first three ways take as starting-points the three types of act or actuality presented by Aristotle in Metaphysics 9.6: that the first way starts from imperfect actuality (motion), the second from secondary actuality (action or efficiency), and TW from primary actuality (being, or substantial actuality). The idea, of course, of a way of proving the existence of a God is that one proceeds from an effect, itself better known to us than its cause, to a knowledge of the existence of the cause. The problem is to develop a vision of the effect as an effect, i.e., a vision such as to reveal dependence on another, and so lead us in knowledge to the existence of that other.