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.
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 one, 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.
Romans chapter one, verse 20 is a quick summary of a longer passage in the Book of Wisdom,
chapter 13, verses one to nine.
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, Aquinas 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.
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've 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 and the world around us.
God is present in things, moving them, causing them, giving them being and directing the
course
of everything.