Can an Atheist Have an Infinite String of Dodges?
by Glenn Smith
The following is the first of Thomas Aquinas’ five ways of
establishing the existence of God. For our immediate purpose, we are merely trying to establish a beginning of causes. That the first cause is known as God, or how or to what
extent we have defined God, is secondary to our immediate discussion. For now,
we are merely interested in establishing a beginning.
Aquinas’ first way, from the Summa Theologica, is as follows:
It is certain, and evident to our senses, that in the world some things are in motion. Now whatever is in motion is put in motion by another, for nothing can be in motion except it is in potentiality to that towards which it is in motion; whereas a thing moves inasmuch as it is in act. For motion is nothing else than the reduction of something from potentiality to actuality. But nothing can be reduced from potentiality to actuality, except by something in a state of actuality. Thus that which is actually hot, as fire, makes wood, which is potentially hot, to be actually hot, and thereby moves and changes it. Now it is not possible that the same thing should be at once in actuality and potentiality in the same respect, but only in different respects. For what is actually hot cannot simultaneously be potentially hot; but it is simultaneously potentially cold. It is therefore impossible that in the same respect and in the same way a thing should be both mover and moved, i.e. that it should move itself. Therefore, whatever is in motion must be put in motion by another. If that by which it is put in motion be itself put in motion, then this also must needs be put in motion by another, and that by another again. But this cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover; seeing that subsequent movers move only inasmuch as they are put in motion by the first mover; as the staff moves only because it is put in motion by the hand. Therefore it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God. (ST, 1.2.3)
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Now many introductory philosophy texts have ridiculed the sentence which says “ But this cannot go on to infinity, because then there would
be no first mover.” The accusation is that Aquinas assumes a first mover without proving there to be one. But this criticism misunderstands Thomas’
meaning of movement, for his context is that of ongoing causation of movement. Thomas gives us an explanation when he states “as the staff moves only because it is put in motion by the hand.”
Assume you are in your car, and pull up to a railroad crossing, and you see a series of boxcars rolling past. It would be absurd to say “The boxcars need no engine,for there could be an infinite series of boxcars.” This is absurd, for boxcars can only be moved, cannot generate movement, and cannot move themselves. If there is movement in the boxcars, there has to be something pulling the boxcars that is much different from a boxcar, something that can cause movement while itself is not being moved by another. So a series of things being moved cannot go on to infinity, for there would be nothing causing the movement in the whole chain…