There is a common notion in the modern world:
That the Catholic concept of the existence of God cannot be proven and is a belief owed entirely to superstition and irrational interpretations of the patterns of reality. A myth created by humanity to explain the unexplainable or to comfort believers and nothing more than that.
The "comfort" hypothesis is easily refuted considering that so many people have suffered torture and execution, and continue to suffer torture and execution, for this belief. The first 31 popes were all martyrs along with all of the apostles save Saint John. Most of them suffered greatly for their Catholicism before dying. The 20th century produced more Catholic martyrs than all others combined. I can personally assert that the belief brings a great deal of anxiety since I live in a society that is increasingly hostile toward those who believe in God, particularly as it is defined by the Catholic Church. People, primarily other Christians in fact, generally don't like Catholics in the country in which I live. At the moment, we aren't being tortured or put to death in this country, but if my belief were strictly based on comfort, I would have let go of it a very long time ago. Still, could God just be a construct of the imagination and its need to assign meaning to whatever it observes? Is it a flight of fancy devoid of reason?
This modern assertion is based largely on a dismissal of a great intellectual tradition present throughout human history as well as, in the present age, the rise of "scientism:" the claim that the only true knowledge is scientific knowledge (ironically, this is a self refuting philosophical claim, not a scientific one.) More than anything, it is the result of the modern person's use of a caricature of God as the starting point for the conversation in favor of what is actually meant when a Catholic uses the term. This caricature of God gives the impression that the thinking Catholic imagines God as "a being" out there in the universe. Perhaps a man with a beard sitting on a cloud or some kind of giant eye looking down at us from outer space. It gives the impression that the thinking Catholic only believes in this weird god-being because he believes in some mystical revelation of its existence that he was told happened and that this belief is maintained in a hokey, made-up religion or recorded in some old book. The scoffer usually fails to attack the actual Catholic idea of God, which begins before there was any revelation and can be discerned by the philosophical and scientific mind before it is ever exposed to the revelation preserved in a religious tradition. The God that is not "a being" but the inventor and the subsistence of the very notion of being.
The true idea of God, perhaps unexpectedly for the modern person, is a philosophical inevitability and it begins with observing the world around us. This is why men like Einstein and Sagan, neither of whom were religious people, still used the term "God." This is not because they were being unscientific and it was certainly not because they had any affinity for religion. It is because they understood that Science and philosophy go hand in hand and the philosophical concept known as "God" is an underpinning of real scientific and philosophical discussion. So what did Einstein and what does a Catholic mean when they say the word "God?" How does one discover this concept without it being a construct of religion?
We live in a universe that is built upon contingency. Everything that happens or exists in the universe has a cause. A specific set of circumstances that must be present for it to exist or take place. A falling rock is contingent upon the existence of both a rock and the force of gravity. The existence of the rock is contingent upon a myriad of forces, laws and materials that make its formation possible. The existence of gravity seems to be inexplicably contingent upon the mass of an object. As you continue to follow these lines, you begin to come to things that, as yet, have no obvious cause. We do not even know where laws come from. Why does an object have mass? Why does a certain mass automatically generate a specific inertial and gravitational attribute in an object? Eerily, no one knows. This alone, obviously, does not prove the existence of God. We may one day, in fact, discover the cause upon which laws are contingent. A new cause to be puzzled about the cause of. The point is that everything in the universe would seem to have a cause, whether we know what it is or not.
It is at this point that the accusers usually expect me to pick a mysterious event or phenomenon that is not yet explained and say something like, "see?! It's God!" Something like, "No one knows why the Big Bang happened! That's because it was God!" Or something like, "You can't explain physical laws! That is because God simply wrote them!" While those things could be true, that isn't the point I'm trying to make here at all and an accuser would be very right in claiming that those assertions would prove nothing as we may yet discover a cause upon which those things are contingent within the measurable universe.
The real point I'm trying to make is, if everything in the universe is contingent upon pre-existing circumstances, this means that the very law of contingency, the rule that states that all things have a cause, must itself have an ultimate cause. If the universe were simply infinite space with an infinite past and infinite future of cause and effect, it would indicate that the universe itself has no cause. Even though space and time seem contingent, there is no original cause to set the chain of events into motion, indicating that contingency is ultimately an illusion. This only moves the target, though. It does not eliminate it. You begin to find new causes here. New platforms upon which the argument can continue to take place. For instance, if it turns out that the contingent universe is ultimately not contingent, this fact now becomes contingent upon a new law that paradoxically dictates that there is no such thing as contingency. We can no longer say that the universe is not a system of contingency because we must now say that its existence is contingent upon this law that states that it is not contingent. Is the law now immune from contingency? To say so would mean it is contingent upon a newly discovered law. One that seems to state that there is a law that is not contingent upon laws. All laws except the law that absolutely governs its existence, which amusingly, refutes its possibility altogether.
The idea that is usually arrived at here is that a non-contingent reality does not seem to work. But neither does a reality with a simply endless parade of causes as this implies that there is no ultimate cause and, therefore, nothing should exist at all. You ultimately arrive at infinite causeless causes.
This leaves us philosophically chained to a single conclusion. That there is an ultimate cause of causality itself. A single causeless cause that exists outside of all ideas, indeed, being the inventor the very idea of ideas. The cause that invented the idea of cause as an original novelty. This causeless cause is naturally not subject to any of the laws of the universe as it is the origin of those laws, including the very concept of contingency.
Some might say that I am breaking my own rules with this idea. That by saying that there is a causeless cause I am defining a law upon which this cause that is immune to contingency is contingent. But that's really just it. We are not talking about a place or a time or a thing that would necessarily have to obey a law to keep from breaking it. To repeat my question from earlier, "is the law itself now immune to contingency?" The answer is both yes and no. This cause does not have to obey a law in order to keep from breaking it. It is the subsistence of law itself. Paradox is its persistent sign. A broken law that is never broken. A burning bush that is never consumed by fire.
We are talking about that from which the notion of causality itself takes its very right to exist. The origin of times, places, and things, not itself a time, a place or a thing. A cause so infinite and so paradoxical as to be describable only through illustration and metaphor and, most importantly, paradox.
It is evident that Catholics have thought about all of this from the beginning. In fact, much of what I am saying is simply extrapolating from Aquinas' "Argument from Contingency" which he wrote a thousand years ago. One of five proofs for God's existence that Aquinas covered a millennium before you were born. And he was building on the backs of others! The conclusion is that, whatever this indescribable causeless cause is, whatever this paradoxical reality beyond realities that is here and now creating the universe is... that is what Catholics call "God."
The Catholic definition of God is that God is "being itself." God is that from which all other notions, ideas, laws, and realities recieve their very capacity to be. This definition does not encompass the totallity of what God is because God is infinite possibility. Not even infinite possibility, but the inventor of the original notion of possibility. Though our definition cannot tell us with totality what God is, it does effectively tell us what God is not. God is not "a being." God is the subsistence of being. God is not "a past event that caused everything." God is that which here and now is inventing the very concept of cause.
My intention here has been to accomplish two things. The first being to show that, for a Catholic, the belief in the existence of God is based on reason, not superstition. The second has been to give a clearer picture of what a Catholic means when he says the word "God." What does any of this say about the expansive revelation from God that the Catholic Church claims to be the custodian of? This is an entirely different argument for another time. One that does not deal so much with whether or not God exists, but rather whether or not He has revealed Himself to His creation... We believe there is considerable evidence that He has.