Marino Ancient & Medieval Philosophy Professor Johnson May 2011

The First Way of Thomas

           

            The text of the body of his argument reads as follows:

"The first and more manifest way is the argument from motion. 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."

(Taken from new advent translation http://www.newadvent.org/summa/1002.htm)

The first problem with Thomas is his somewhat confusing language, therefore it must be cleared up that when he speaks of something moving from potentiality to actuality he speaks in terms of its being in motion, and not of simply being. That is, the potential for something to be in motion versus something actually being in motion. A thing’s being in a state of potentiality in one aspect of motion does not restrict it from being actual in another aspect, as opposed to something being in a state of potentiality for a state of being which does negate all aspects of actuality. Also, the word potential, as he uses it does not mean simply the ability to be something, but also as the opposite of actually being so. Therefore, a thing cannot be in a potential state of being hot if it is on fire, for it is actually hot-but it is potentially cold, for one could pour ice-water on it. It is also unclear what Thomas means when he says “But nothing can be reduced from potentiality to actuality, except by something in a state of actuality.” We must remember here how Thomas uses the words potential and actual. A thing which is not hot cannot cause something to become hot, for it is not hot itself. Therefore, something which is potentially hot cannot cause itself to become actually hot, for it is not hot, and it requires something which is actually hot to cause it to be reduced from potentiality to actuality. These points being cleared up, let's look at the actual form of his argument.

1. "It is certain, and evident to our senses, that in the world some things are in motion."

2. Things move when potential motion becomes actual motion.

3. "But nothing can be reduced from potentiality to actuality, except by something in a state of actuality."

4." Now it is not possible that the same thing should be at once in actuality and potentiality in the same respect.."

5."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."

6."Therefore, whatever is in motion must be put in motion by another."

7.Every moving thing must be moved by a prior moving thing, which was moved by a prior moving thing, "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."

8."Therefore it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God."

            Ignoring the irrationality of having the foundation of a logical proof of God's existence rest on our notedly flawed sensory perception, Thomas’ arguments rely heavily on inductive reasoning. He argues that all things must be caused to move by a separate moving thing(3) and that there can be no thing which moves itself(5). While these claims seem intuitively true, and indeed agree with our experiences, they are not logically sound. Simply because we do not observe things to move themselves, it does not follow that they cannot. In fact, Thomas later contradicts this premise, stating that there is such a being as an unmoved mover. Why then, are we justified in believeing that there are not many unmoved movers, constantly acting internally on themselves in way unbeknownst to us?

            However, even if you accept the testimony of your senses, and conclusions based on limited experience, you have only up to step six. In premise seven, Thomas claims to prove the first mover by pointing to the impossibility of an infinite regress. However, it is equally implausible to our thinking that there be an unmoved mover as an infinite regress. Furthermore, Thomas relies on circular logic to prove an unmoved mover by citing the impossibility of an infinite regress, which is impossible “because then there would be no first (unmoved) mover.”

Failing to prove an unmoved mover, Thomas then claims that this unmoved mover is God. Even if we are to believe that there is only one unmoved mover, why must this being be all-powerful, absolutely good and eternal?

            Thomas’ argument is filled with specious reasoning, and cannot stand as a logical proof of God’s existence. What Thomas really proves here is the inadequacy of this technique, and the impossibility of producing a logical proof for an infinite being that defies logic.