The Catholic Tradition:
Which God don't you believe in?
"I don't believe in God?" "God does not exist." What do people mean when they say these
things? Often, people who say this do not really understand what Catholics mean by the
proposition "God exists." So, when dealing with atheists, it becomes very important to clarify,
"What do you mean by God?" What do you mean by "exist?" You may find out that the atheist is
rejecting a phantom, a "god" Catholics also reject.
Let me illustrate. I read once about a camp for children run by atheists. Their goal was to
inoculate children against religious belief, and they used a number of techniques. One stuck in
my memory. The children were given the task of proving that unicorns do not exist.
Once you begin the task, you realize it is impossible. There is no way to prove that unicorns
don't exist. The best you can do is show that there is no good reason to believe in unicorns. The
point of the exercise should be obvious. The camp counselors wanted the children to think of
God (or the gods) like unicorns: mythical beings for whom there is no scientific or empirical
The problem with this plan is that it totally misrepresents what Catholics mean by the word
"God." Catholic philosophers go to great pains to explain that God is not a being among other
beings. He does not belong to the genus or class "things that exist." In fact, he is not in any genus
or class at all. (For example, see St. Thomas Summa theologica I. 3.5.) If there were a unicorn, it
would be one thing among many - like a squirrel, or a fish, or a stone. Similarly, if the Greek
gods existed (Zeus, Hera, Hercules), they would also be things, substances, beings. But, St.
Thomas says, this does not at all capture what we mean by the word God.
The unicorn exercise also misrepresents what we mean by exists. Many atheists assume that
there is only one way that a thing can exist - by taking up space, the way a unicorn in the forest
would take up space (and be susceptible to scientific investigation) if it were to exist. This is
what Aristotle would have called a substance. But this is clearly not the only way we can think
of existence. Consider the following:
Numerical relations are real - they exist - in a way, but not in the way a cat or a unicorn would
exist. Numerical relations are abstract entities. Attributes or qualities (accidents) are also real things like tall, green, round - but they exists differently from substances. The Mind is real - a
conscious entity constituted by concepts, intentions, reasons, memory and personal identity, but
the mind does not exist at all in the same way that bricks or dogs or even hearts and livers exists.
Minds depend on matter (the brain) for their operation, but they cannot be reduced to matter. The
mind is an immaterial reality- (If you doubt this, try explaining how mental concepts like
democracy, or the quadratic formula, or logical operations are material entities.)
These distinctions are very important when we explain to atheists what we mean by the words
"God exists." At the very least, when we say "God" we mean the ultimate explanation of all
beings, the ground of their intelligibility. And so to say, "I don't believe in God" is as much to
say, "I don't think that reality is intelligible. There are no ultimate explanations. Reality is
absurd." Most modern atheists (with their love of science) are not willing to go there. The real
debate, therefore, is not such much whether God (so defined) exists, but what God is like? Is
ultimate reality (God) complex, material, and random? Or is it immaterial, simple (indivisible),
and purposeful?
Likewise, when we say that God exists - we do not mean that he exists in the manner of a
material substance. Material substances are subject to change, they are composed of parts, and
they depend on a certain bodily integrity or form for their existence. (To illustrate, if you smash a
cat into something shaped like a pancake, it stops being a cat.) But this is not what exists means
when applied to God. God's existence is more like (but not exactly like) that of minds and
abstract entities. In technical terms, we speak of God as Subsistent Being - not a being, but the
ground of all being, the ultimate fact or reason for finite beings.
Proving the existence of God (so defined) boils down to showing that material substances cannot
be the source of their own existence. They depend, here and now, on deeper and deeper layers of
reality that become less and less like material substances the more you investigate them. Even an
infinite number of material substances in a causal chain would still depend on deeper realities like being and causation itself - to explain their existence. This reflection leads us to a reality
that is not subject to change (for there is nothing prior that could cause it to change), that is
simple, that has no parts (for there is nothing prior that could explain its composition), and that is
purposeful or goal-directed - inasmuch as reality proceeds from it as a consistent effect from a
cause. We are led to a reality in which existence itself does not depend on form (the way a cat
depends on cat-form to exist), but to a reality in which being and essence are one.
What do you mean by God? What do you mean by exist? Our philosophical answer to these
questions does not bring us all the way to the God of Catholic Christianity. There are still many
things that Catholics believe that cannot be proved by reason. But the Catholic doctrine of God
presupposes the philosophical definition. (So says the First Vatican Council.) We cannot have a
rational discussion with an atheist if we don't understand this. In some cases, the atheist has
never really considered the case for God. He is rejecting a God we dont' believe in either. Only
after we establish this can we move on to considering the case for Catholic revelation.