St. Thomas Aquinas

St. Thomas Aquinas' First Two Ways in Proving the Existence of God

It is my view that God exists, and I think that Aquinas' first two ways presents a

successful argument for the existence of God. No doubt, the arguments have weak points

which are subjected to criticism but nonetheless, in my opinion, these propositions by

Aquinas do indeed accomplish their purpose in establishing the existence of a Greatest

Conceivable Being that is the unmoved mover and uncaused cause. I believe that this

ultimate Being is unchanging and started the universe, time and all matter and concepts

of existence. In my view, this Being is what we understand to be God.

St. Thomas Aquinas recognized that there were some people who doubted the

existence of God because, to them, logic did not allow for or explain God's existence. His

first two ways are two proofs based on logic and observation of nature in proving God's

existence to those who could not accept or believe God on faith alone. Aquinas' first way

is based on motion. He calls it the most obvious way. This first argument, the Argument

from Motion, tries to prove the existence of God as the first mover which is unmoved.

Now, it is certain as a matter of sense-observation that some things in this world are in

motion. Whatever is in motion, Aquinas states, is moved by something else. Aquinas then

defines one type of motion as the reduction of something from potentiality to actuality,

and says that nothing can make this movement except by something that is already in

actuality in the same respect as the first object is in potentiality. For example, something

which is actually hot, like fire, makes something which is potentially hot, like wood, to

be actually hot. In this way the fire moves and alters the wood. Now, it is not possible for

the same thing to be, at the same time and same respect, in actuality and in potentiality.

For instance, what is actually hot cannot simultaneously be potentially hot, though it may

simultaneously be potentially cold. So, it is impossible that in the same respect and same

manner anything should be both mover and moved. In this, Aquinas means that nothing

can move itself. Therefore, if something is in motion, it must have been put in motion by

something else, which must have been put in motion by yet another thing, and so on.

However, this cannot go on to infinity because there would never have been a first mover

and, consequently, no subsequent movers. After all, second movers do not move except

when moved by a first mover, just as a stick does not move anything except when moved

by a hand. Thus, this leads to the conclusion that there is a first mover which is not

moved by anything, and this first mover is what we understand to be God.

Summarizing Aquinas' first way, the argument states that objects are in motion,

and if something is in motion, then it must be caused to be in motion by something

outside of itself. That is, an object in motion is put in motion by some other object or

force. There can be no infinite chain of movers/movees so there is a first, unmoved

mover. Therefore, in conclusion, the unmoved mover exists and is called God.

Aquinas' second way in proving God's existence is based on the nature of

efficient causation. Now, causation itself is "making to be" in the sense that the cause

makes there be the result. Efficient causation, however, is the production of the result, or

the activation from being merely possible or potential into accomplished fact. Thus, the

efficient cause is what brings about the result to be effectively realized as actual. In the

observable world we discover an order of efficient causes, but no case is found, or ever

could be found, of something efficiently causing itself. Such a thing would have to be

prior to itself, which is impossible. Now, it is impossible to go on forever in a series of

efficient causes. This is because in every ordered series of efficient causes the first

member of the series causes the intermediate member or members (whether the

intermediate be one or many members), which in turn cause the final member. If you

eliminate a cause you eliminate its effects, so there will not be final or intermediate

members in the series unless there is a first member. Given if the series goes on forever,

then there will be no first efficient cause, and so there will be no intermediate efficient

causes and no final/last effect, and this would be an open mistake which is obviously

false.