God Does Exist and Thomas Can Prove It

What if I told you that God exists whether you believe in Him or not? What if I told you that you don’t need faith to know God exists?  What if I told you that logic and reason lead us to God?  All of these claims were made almost 800 years ago and the answers have been at our fingertips without most of us noticing.

Today in the Catholic Church we celebrate the feast day of St. Thomas Aquinas, 13th century Dominican and Doctor of the Church.  He is one of the most prolific theologian/philosophers to ever live and, in my opinion, one of the most under appreciated.  In less than 40 years St. Thomas wrote more than any theologian could hope to write in a lifetime’s worth of work.  His most well-known work, Summa Theologica, is a mere summary of theology that amounts to almost one million words… about the same as the entire Harry Potter series.  Many Catholics know who St. Thomas Aquinas is, but know very little about his teaching.  Additionally, many college philosophy classes do not touch his work because he is a man of faith.  I want to take a tiny sample from this vast ocean of St. Thomas’s theology and philosophy by looking at his first argument for the existence of God.

St Thomas Aquinas has five arguments for the existence of God in the Summa which are often referred to as the Five Ways.  It is very important to understand that these arguments are philosophical arguments based on reason, thus, these arguments do not require faith to be held as true.  I will say more about this at the end, but let’s get to the first argument.

The First Way of St. Thomas Aquinas is the Argument from Motion.  This first argument begins with the observation that there are things in the world that are in motion.  Seems pretty obvious, I hope, but have you ever asked where this motion comes from?  This is a question we seem to be asking less than before: where does this thing or that thing come from?  Most things now come from Amazon, however, that is not where motion comes from.  Where does motion come from?

The obvious answer is from something else.  Isaac Newton gave us this idea in his very first law of motion.  He says that an object at rest tends to stay at rest and an object in motion tends to stay in motion UNLESS another force acts to change that motion (or lack thereof).  Every object that has motion has received it from something else that has motion; if it had not, it would remain at rest.  St. Thomas and Isaac Newton tell us that a thing (creature or object) can not be the cause of its own motion.  In the words of St. Thomas, “nothing can be reduced from potentiality to actuality, except by something in a state of actuality” (ST I, q. 2, a. 3).  An object is either in motion (actuality) or not in motion (potentiality).  Something can not change itself from potential to actual because is cannot give what it does not have.  Therefore, if an object is in motion then it necessarily received that motion from another object that was in motion.

For example, imagine a golf ball sitting on a tee.  The golf ball will remain on that tee until some other force acts upon it (wind, golf club, a squirrel, etc.).  The golf ball is in a state of potentiality which means that the only thing that can cause it to move is something other than itself.  All of the sudden a golf club comes out of nowhere, smacks the golf ball, and sends it hurling down the fairway!  The distance the golf ball travels depends on the amount of force it was given by the golf club and how much force the ball transfers to the ground and grass that it comes into contact with.  This is day one physics stuff… BUT where did the golf club get its motion from?  Well, Tiger Woods of course! BUT where did Tiger Woods get his motion from? Well, he gets it from a complex biological process that began with his parents.  BUT where did his parents get their motion from?

You can quickly see how this questioning could go on forever.  What we end up with is a seemingly infinite regression of motion.  This regression, however, cannot be infinite because we would end up with no source of motion.  As we showed above, there must be a source of motion because we can see that there is motion in the world and nothing can be the cause of its own motion.  There must be a first mover, who is put in motion by no other, in order for motion to exist at all.  It is this first mover whom we call God. 

This first argument from St. Thomas Aquinas uses reason alone to show that God must exist.  While this does not tell us much about who God is, it does show us the necessity of a first mover.  Combined with the other four ways, we come to see that the existence of God is not a question of faith.  It is something that can be proven by reason alone.  Faith begins where reason can no longer prove.  Our faith, therefore, is not in the fact that God exists; Our faith is trusting that what He tells us is true.  We can see that God exists through reason, but it is through faith that we come to see that God loves us and longs for an intimate relationship with us.


Below is a full excerpt from St. Thomas’s Summa Theologica that was used in this post.

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.   – (Summa Theologica Part I, Question 2, Article 3)

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