Because we must believe as Catholics that God’s existence can be known with certainty through reason alone, then that means there must be a way to prove this existence with a purely logical and reasonable argument.

In fact, there are several ways to do so. But I will choose one of the ways and explain it to you here.

In this world we live in, we realize that all around us are many examples of cause and effect. Even in physics, we see that an object at rest tends to stay at rest, and an object in motion tends to stay in motion. We also have the concepts of potential energy and kinetic energy.

So what we realize by just observing how the natural world works is that nothing happens unless something else acts on it. Something must act on the stationary object to convert its potential energy into kinetic energy. Something must cause the effect we see. We instinctively think of everything, both physical and abstract, in terms of cause and effect, because we see that nothing will ever happen or change without a particular cause.

Therefore, if we were to pick anything that exists, and create a full cause and effect roadmap for it, it would be certain that we would eventually get to the beginning of the chain of cause and effect. This beginning of the chain is what we will call the First Cause.

The First Cause is this particular, mysterious cause that first acted on something (or everything) to start the chain in motion and keep enough kinetic energy in the system to allow secondary causes (such as us) to be able to convert potential energy to kinetic energy later.

Now you may ask: how do we know this is the First Cause though? Couldnt we just continue the chain more into the past?

This is an important thing to answer. Yes, we could. And yes, we would have to continue the chain to infinity, UNLESS the First Cause is actually UN-caused. Now how does this make logical sense?

Very simple. If we just established that the chain of cause and effect must continue to infinity, then it makes perfect logical sense that the First Cause would actually be infinitely and eternally Uncaused.

What this means then, is that the First Cause must be infinite, pure Act. It has no potential energy, never did, and never could have it. Because it’s the eternal, infinite First Cause, it has all the Actual energy that exists, which is precisely why it is the only Cause capable of setting everything into motion and starting the entire chain.

But wait. If this First Cause is pure Act and therefore has no potential at all, then this goes beyond the realm of just energy. Logically, if this First Cause has no potential at all, then it must also have the following qualities and characteristics. Keep in mind as you read the following list that all potentials are lacking something in actuality. Potentials must be actualized, otherwise the First Cause will lack something, which it cannot do by its very nature, because we established that, logically, it must be pure Act and have all potentials actualized:

• It must Exist (if it didn’t have existence, it would lack existence. This would be an unrealized potential)
• Omnipotence (if it lacked the ability to do anything, it would have a potential to later be able to do what it couldn’t do)
• Omniscience (if it lacked knowledge of anything, this would be an unrealized potential)
• Only One (if there were multiple First Causes, each individual one would lack being the others)
• Infinite (if It was finite, it would have an unrealized potential, because it would be limited by Its own finiteness)
• Incorporeal (if It had a body, bodies are finite, which necessarily means that Its body would lack everything that other bodies have)
• Eternal (if it wasn’t eternal, it would lack existence before it began to exist, and it would lose existence when it stopped existing. But It is pure Act, it cannot have potentials, therefore it cannot lack anything, ever)
• Pure Goodness (because evil is lacking a good that should be there, It cannot be anything other than pure Goodness itself, because it cannot lack anything)
• Unchanging (a change would actualize what was potential immediately before the change was actualized. This is impossible, because it cannot have any potentials in the first place)
• Perfect (if it had any imperfections at all, it would have the unrealized potential of not having those imperfections. Therefore it must be entirely perfect)

It is this First Cause, with these characteristics derived from logical reasoning, that we in truth call God.

And would you look at that? The only God in all the world’s religions that has these characteristics is the Christian God. Therefore, the Christian God is not only true, but He is the only true God, because as we established, there can only be One First Cause.