Thomas Aquinas's famous work called the Summa Theologiae has three main parts. The first part
deals with the presence of God in creation. The second part deals with the presence of God by
grace in the souls of the just. And the third part deals with the presence of God in Christ
and in his mystical body, the Church. The whole thing is really an extended meditation on the
presence of God. But one of the greatest questions of all times is whether God exists.
And Thomas takes the question head-on with his famous five ways,
or five proofs, for the existence of God.
In this episode, we will give a brief sketch of the five ways.
But let us first ask how human beings can know the existence of God.
One way to know God's existence is by taking it on faith from what the Bible says. But Thomas is
well aware that the Bible itself tells us that there's another way to know the existence of God.
In Romans chapter 1, verse 20, St. Paul tells us that the existence of God is known to everyone,
at least in a general and confused sort of way, from the beauty and goodness of the natural world.
And Romans chapter 1, verse 20, is a quick summary of a longer passage in the Book of Wisdom,
chapter 13, verses 1 to 9. The two passages tell us to expect to find human beings who have never
even read the Bible, but know that God exists just from their experience and rational reflection
upon the natural world. Now, when Aquinas turned to the writings of ancient pagan philosophers,
he found exactly that. He found people who had never read the Bible, but who had given
serious arguments for the existence of God. The writings of ancient pagan philosophers
confirmed the biblical teaching that it is possible for human beings to know the existence
of God without ever even having read the Bible. For both of these reasons, Aquinas taught that
human beings have a natural knowledge of God, or to put it another way, that we can know the
existence of God by using our natural reason or human intelligence. That is the kind of knowledge
we're exploring here, our natural knowledge of God. Now, Thomas did not say that our natural
knowledge of God was always explicit, clear, or easy to come by. He did not affirm that the existence
of God was undeniable. Rather, he thought of the natural knowledge of God as falling on a spectrum
of cognitive development. Everyone has a common and confused knowledge of God's existence, but
like any other form of knowledge, this common and confused knowledge of God is open to development
for those who have the time, interest, and intellectual gifts for developing it. Thomas
also realized that it was hard to develop our natural knowledge of God, and many factors stand
in the way. Depending on cultural circumstances, people will develop it more or less, but generally
not to its fullest perfection. But, he says, a few people, after a long time, and still with some
errors mixed in, will develop their natural knowledge of God to such an extent that they
can offer philosophically rigorous proofs for the existence of God, and answer all objections to
those proofs with great dialectical skill. This is the task he takes up in the famous passage on the
five ways, and in other more extensive writings of his on the topic. So, how exactly do we know the
existence of God? The basic principle behind the five ways is that we know the existence of God
from our experience of the world of nature, and looking for an ultimate explanation of it. We use
the same kind of reasoning that we use when we know the existence of any invisible cause
from visible effects. For example, if I'm driving down the freeway and see a billowing cloud of
smoke coming up from the horizon, I can infer there must be a fire, even if I do not see the fire,
even if it's blocked from my view. The fire is invisible, but the smoke it produces is not,
and I know the existence of the invisible cause from the visible effect. Or similarly, if I wake
up one morning with a sore throat, I infer that I have some kind of infection or virus. I do not see
the infection or the virus. The cause of the sore throat is invisible, but I know that it's there by
reasoning from the experience of the symptoms. So it is with our knowledge of God. What we see or
experience around us is the natural world. God is invisible. We don't see him, but from what we do
see and experience of the natural world, we can infer that something must be behind it all.
Something is responsible for the greatness, the beauty, the order of the world. Aquinas thought
that this inference from the order of the world to the existence of something responsible for
the order of the world was so fundamental that nearly all human beings reason this way.
But he also realized that this inference or argument was something like a seed. The seed can
develop and grow through study and the application of the mind to the many philosophical issues
involved in making the inference. But the seed can also be crushed by attachment to sin,
willful self-denial, false philosophies, and other adverse conditions that ruin it.
So we're not committed to saying that agnosticism and atheism are impossible. They might even become
prevalent in some societies. But we are committed to saying that natural theology is possible for
human beings. And Thomas Aquinas is an example of someone who developed this natural knowledge of
God to an extremely high degree. What he did was take the general argument from the order of nature
and think it through along much more specific lines. To spell this out, let us give a sketch
of each of the five ways. In the first way, we start with our experience of the order in the
motion or change of things around us in nature. And careful study of what motion and change are
leads us to conclude that there must be a first mover or unmoved mover or an ultimate source of
change in things. In the second way, we start with our experience of an order of cause and
effect in things around us. When we reflect carefully on what causality is, we learn that
in order for there to be causes at work, there must be a first cause or uncaused cause. In the
third way, we start by considering the order of contingent beings, things that exist but do not
have to exist. When we reflect on things that exist but do not have to exist, we naturally ask,
why do they exist? This leads to the conclusion that there must be a source of the very existence
of contingent beings, and the source cannot not exist. The source simply is. In the fourth way,
we look at how things around us exist in grades of perfection, and the grades of perfection lead
to the conclusion that there must be a perfect being, the source of being in everything else.
And finally, in the fifth way, we find in nature that things without intelligence act for the sake
of ends. Honeybees work to produce honey even though they do not have intelligence, properly
speaking. Things without intelligence cannot work for the sake of an end unless a higher intelligence
is directing them. This leads us to conclude that there must be a supreme mind or intelligence
behind it all. Now what I have given here are just sketches of the arguments, and one can spend a
lifetime considering all the issues surrounding them. But even the sketches give us a way to begin
meditating on the presence of God in the world around us. God is present in things, moving them,
causing them, giving them being, and directing the course of everything.
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