monstrate in a rational manner the existence of God. Aquinas accepts the existence of God as a matter of faith in his role as a Christian and a theologian, but as a philosopher he offers logical proof that would appeal to the skeptical mind. The article in Summa consists of five short, almost cursory proofs, totalling less than three pages. Yet, this remains one of the most influential pieces of scholastic theology ever written. Aquinas' general method was to try to show how God can be known from his effects, meaning from the world around us, and he limited himself, by and large, to arguments based on reason rather than revelation.
The Five Ways, as they are called, are grounded in Aristotle's Metaphysics. Aquinas' mentor, Albert the Great, was one of the first scholars to put pagan philosophy to work in the service of Catholic theology, and Aquinas carried this approach to its zenith (Gratsch xiv). It has been argued that the Five Ways are structured in such a way as to reflect Aristotle's Doctrine of the Four Causes: the First and Second Ways deal with two different aspects of efficient causality; the Third way deals with material causality; the Fourth way deals with formal causality; and the Fifth way deals with final causality (Kenney 36).
In the Second Way, Aquinas argues again from the fact that the things of this world are in motion. We can see this from the evidence of our senses, though the issue should be raised as to whether sensory information can be fully trusted. The fact that something is moving, however, means that there is something to cause it to move. The relationship between mover and moved is a cause-and-effect relationship, and the world involves a series of cause-and-effect relationships. Wherever there is such a series of causes and effects, the series must be caused by a being who is itself uncaused, otherwise we have an infinite regress, which Thomas finds intellectually repugnant. The Second...