One of the questions in the air for Contemporary Thomism is what STA means by calling his theistic arguments the five ways. Regretfully to those who claim that he called them ways because he didn’t want to call them proofs, this sort of distinction was unknown to STA, and the ways are said to prove (probare) God exists. There is much more to be said in defense of the idea that STA called them ways because he saw them as all modes of a single form or template, differing only by their sensible points of departure.
The template looks something like this:
Whatever is X-ing is X-ed by another
X-ing things that are X-ed by another are caused by what’s ~X-ed.
A ~X-ed cause of X-ing is God.
You have to massage the mode of signification in order to make the paradigm work, but the first premise is established for all the proofs follows argumentation like this:
1.) What is in motion is potential
The potential as such is actualized by another
2.) Whatever has an agent cause is being caused by another.
3.) Whatever is contingent is caused by another, and so also what is necessary by another
4) Whatever is more or less perfect is caused by the maximal.
5.) Whatever acts for an end without intelligence is caused by what acts with it.
In the last two ways, the existence of God is given from the moment you establish this “other”, but in the first three ways there is the additional step of having denying infinite regress, though our present ideas of infinity are so opposed to STA’s that we can present his thought better by saying, with Leibniz, that even if there were infinite things caused by another, all the causes of the event could not have this character. You might very well have infinite copies of the choir program, but not all the choir programs could have been copies.
The third premise is never adequately explicated for modern taste, but we tend to give the fifth way a pass so far as it establishes some intelligence beyond nature. But they establish in turn a substance that (1) arose from no previous potentials and has no further possibilities to actualize (2) has no source of its existence (3) is a necessary being and (4) excels all other substances in good, truth, dignity, etc.