Expound and Critically Asses One or More of Aquinas' Five Proofs of God's Existence

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28/11/02                              Luke Bell

Metaphysics and Religion

Expound and Critically Asses One or More of Aquinas’ Five Proofs of God’s Existence

St. Thomas Aquinas, a thirteenth century theologian and author of Summa Theologiae, laid out five proofs or ways for the existence of God. Unlike St. Anselm’s ontological account of God’s existence which is totally a priori, Aquinas lays out his proofs based on premises that are derived entirely from our experiences of the world or empirical evidence. This paper will concentrate on the first three ways that are centred on the principle of cause. This essay will show that although many of his arguments and the arguments that followed on from him are compelling they are not conclusive proofs of God’s existence.

The first three ways are very similar and can be grouped together under the category of the cosmological argument. Aquinas built further upon what both Plato and Aristotle believed about a prime or self mover. The argument relies upon these premises: Nothing that moved or any effect would be present in the world if it were not for what caused the movement or the effect. Every event in the world is due to some prior cause. There must have been some cause that started everything off that is the cause of itself or the self mover. He argued the same point from contingency saying that everything depends on something for existence. There must be one independent thing that all other contingent things depend on.

Aquinas splits this up into three arguments that are slightly different and add their own distinct slant to the cosmological argument. “The first and quite obvious way is taken from the consideration of motion” [Western Philosophy An Anthology – Edited By John Cottingham – Blackwell Publishers, 1st Edition, 1996 – Part 5, Chapter 2 – From Summa Theologiae] This idea of motion is that we get from our senses. As far as we have seen in the past all things that are in motion have been set in motion by something else. Nothing moves independent from a mover. “Now it is not possible for the same thing to be, at the same time and the same respect, both in actuality and potentiality.” [Western Philosophy An Anthology – Edited By John Cottingham – Blackwell Publishers, 1st Edition, 1996 – Part 5, Chapter 2 – From Summa Theologiae] In other words Aquinas is saying that it is impossible for something to move itself because energy for movement is always taken from somewhere else. For this phenomenon to be explained, however, there must be a first or original mover that transcends the normal universal order of mover and moved. This, according to Aquinas, we call God.

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The second way is very similar to the first but adds the idea of cause and effect. Again we get the premise from what we see around us, according to Aquinas “an order of efficient causes.”  For Aquinas it is impossible for something to be the cause of itself because this would mean an object being prior to itself, a concept that does not make sense in a universe governed by time. There must therefore have been something outside of time that was the first cause that set the chain in motion.

The last of Aquinas’ interpretations of the cosmological ...

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