Aquinas’s ‘Five Ways’
Jeff Speaks
January 11, 2005
1 The argument from change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 The argument from causation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3 The argument from necessity and possibility . . . . . . . . . . . . . . . . . . . . . . . . 2
4 The argument from gradations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5 The argument from the governance of the world . . . . . . . . . . . . . . . . . . . . . . 3
Aquinas presents a different way of arguing for the existence of God. It was a feature of Anselm’s
argument that its premises did not seem to rely on any facts about how the world is; the proof
proceeded solely on the basis of the fact that we can imagine a certain sort of being. Aquinas’s
arguments, which are often called versions of the cosmological argument, begin with certain very
general facts about the universe, and argue from these to the existence of God.
He presents five such arguments, which we will discuss in turn.
1 The argument from change
Aquinas’s first argument is based on the idea that the fact that things change shows that God
must exist. The argument appears to run as follows:
1. Whenever something changes, it moves from potentially having a
property to actually having the property.
2. Whenever something moves from potentially having a property to
actually having that property, this must have been brought about
by something which actually has the property.
3. Whenever something changes, this change must have been brought
about by something which actually has the property which is ac-
quired by the object that changes. (follows from 1,2)
4. Nothing can simultaneously both potentially and actually have a
certain property.
5. Whenever something changes, this change must have been brought
about by something else. (follows from 3,4)
6. Some things change.
7. The chain connecting things which change and things which ini-
tiate the changes cannot be infinite.
C. There is a first mover, which initiates change but is not itself
changed. (follows from 5,6,7)
A worry about this argument: it does not seem to show that there is a unique first mover.
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