Kenny, to emphasize what Byblos has said, metaphysical proofs are analogous to geometric proofs. Suppose I were to ask you to provethe law of sines (if one angle is obtuse, then the center of the circle lies outside the triangle). You would respond with something like this:
Suppose you wrote that and I asked for "evidence" for it being true. If I did that, you would rightly conclude that I don't understand how geometry works. Worse, that I don't understand how basic logic works. (If, by the way, you want something easier,
here's a proof that the sum of the angles in a triangle always equals 180 degrees.)
It is just so with a metaphysical proof. Such proofs are not "scientific" in that they do not rely on probabilities or measurements that are subject to interpretation. They are much more stringent. Like geometric proofs, they require absolute
demonstration. Aquinas' First Way is just such a demonstration. In review, they are:
- 1. Some things in the world are changing;
2. Anything that is changing is being changed by something else;
3. But this something else, if it is being changed, is also being changed by something else, and so on;
4. This series of things being changed by something else else cannot be endless;
5. Therefore, there must be a first cause of change which is itself unchanging; this we understand to be God.
(1) is the given. All I have done here is change the word "motion" to "change" (with relevant grammatical changes) to make what Thomas is sayng clearer to you. There are reasons that "motion" is still a better translation, but let that pass for now. Just take it on the authority of someone who wrote their master's thesis on this subject that "change" works. If you absolutely insist on a proper discussion of the proper usage of "motion," see my thesis
here, starting on page six, where you will find a full discussion on the meaning of the words "actuality," "potentiality," "motion," and "change," and the relevant Greek and Latin words behind each.
Anyway, (2) is a metaphysical fact easily demonstrated - there are only three logical possibilities to account for change: a) that something is being changed by nothing; b) that something is changing itself; or c) that something is being changed by something else. Both (a) and (b) are self-contradictory, and therefore (c) is and must be true. (3) is simply the logical consequent of (1) and (2). (4) is true given the nature of the kind of causal chain Thomas has in mind, namely, an essentially ordered causal chain. Byblos has offered you some illustrations to this end, but to add another (which I take from Feser), imagine a paint brush with a very, very long handle--so long, in fact, that you cannot see the hand that holds it. And yet, the paint brush is, in fact, painting the wall. Could an infinitely long handle account for the up and down movement of the brush? Of course not. At some point, you have to have a principle of motion, something that is causing the change, whereby the handle is simply an
instrument by which the thing causing the change (a hand somewhere) is USING it--the handle--to bring about the desired effect. In other words, for any essentially ordered series of changes, there MUST be a first changer. Again, there is no question
that a first changer exists. The question is the
nature of this changer. From (1)-(4), we conclude something about that changer--namely, that it is not being changed in any way whatsoever.
In this thread, Mallz and Byblos have been very patient with you. Both have shown you a
proof for God's existence. You're failure to understand their approach is something you need to work to correct.