Another old post revived; my Philosophy 101 class is going over Aristotle and Aquinas:
In St. Thomas Aquinas' Five Ways, we find the most evident way is the argument from motion, establishing the existence of an unmoved mover. Let me present a version of the argument as follows:
1. At least one thing, call it X, is in motion.
2. If X is in motion, then its motion must be caused.
3. If X's motion is caused, then the cause of that motion must be either a) a series of movers which are themselves moving or b) a series of movers that contains at least one unmoved mover.
4. A series of moved movers, even if it is an infinite series, cannot explain the motion of X.
5. Therefore, the motion of X must be explained in terms of the existence of an unmoved mover.
6. That which does not move but causes the motion of all other things deserves to be called God.
7. Therefore, God exists.
If we look at this argument, premise 1 seems undoubtable. Let us grant that the motion of X must be caused. The options in 3 look exhaustive. I'm going to grant 6 for the sake of argument. Mind you, we're a long way from John 3:16. But it does lead us in the direction of a belief in something non-physical on which the universe depends. But how about 4. Why does 4 seem unsatisfactory?
Well, put something somewhere, say, a five-dollar bill on top of your dresser. Now come back the next day, and see if it is still there. If you see it still there, you don't need an explanation. It is where you expected to find it. If it is gone, we need an explanation. Somebody removed the bill. So, we are inclined, at least initially, to suppose that rest needs no explanation, but motion does. Hence an infinite series of moved movers doesn't do the explanatory job needed, and you need an unmoved mover.
Or do you? Perhaps we think this way because we are accustomed to living in a gravitational field, called planet earth. But if we didn't live in a gravitational field, but lived on the space station, we would expect things to be moving, and we would have to explain why things get stopped.
So the idea that motion stands in special need of explanation, while the absence of motion does not, is an idea that modern science seems to reject. Without this assumption, the argument to the Unmoved Mover fails.
Or does it? Are there any good Thomists (followers of St. Thomas Aquinas) out there who can explain to me what I might be missing?