Is it rational to believe in God?

Many people think that faith and reason are opposites; that belief in God and tough-minded logical reasoning are like oil and water. They are wrong. Belief in God is far more rational than atheism.

Logic can show that there is a God. If you look at the universe with common sense and an open mind, you’ll find that it’s full of God’s fingerprints.

A good place to start is with an argument by Thomas Aquinas, the great 13th century philosopher and theologian.

The argument starts with the not very startling observation that things move. But nothing moves for no reason. Something must cause that movement. And whatever caused that, must be caused by something else, and so on. But this causal chain cannot go backwards forever. It must have a beginning. There must be an Unmoved Mover to begin all the motion in the universe: a first domino to start the whole chain moving, since mere matter never moves itself.

A modern objection to this argument is that some movements things in quantum mechanics -- radioactive decay, for example -- have no discernible cause, but hang on a second. Just because scientists don’t see a cause, doesn’t mean there isn’t one. It just means science hasn’t found it yet. Maybe some day they will. But then there will have to be a new cause to explain that one. And so on and so on. But science will never find the first cause. That’s no knock on science. It simply means that a first cause lies outside the realm of science.

Another way to explain this argument is that everything that begins must have a cause. Nothing can come from nothing. So if there is no first cause, there can’t be second causes. Or anything at all. In other words, if there’s no creator, there can’t be a universe.

But, what if the universe were infinitely old, you might ask? Well, all scientists today agree that the universe is not infinitely old, that it had a beginning in the Big Bang. 

If the universe had a beginning, then it didn’t have to exist. And things which don’t have to exist, must have a cause.

There’s confirmation of this argument from Big Bang Cosmology. We now know that all matter, that is, the whole universe, came into existence some 13.7 billion years ago and it’s been expanding and cooling ever since. No scientist doubts that anymore, even though before it was scientifically proved, atheists called it “creationism in disguise.”

Now add to this premise, a very logical second premise -- the principal of causality that nothing begins without an adequate cause. And you get the conclusion that since there was a Big Bang, there must be a Big Banger.

But is this Big Banger God?

Why couldn’t it be just another universe? Because Einstein’s General Theory of Relativity says that all time is relative to matter and since all matter began 13.7 billion years ago, so did all time. So there’s no time before the Big Bang.

And even if there is time before the Big Bang, even if there is a multi-verse, that is, many universes with many Big Bangs, as String Theory says is mathematically possible, that too must have a beginning. An absolute beginning is what most people mean by God.

Yet, some atheists find the existence of an infinite number of other universes more rational than the existence of a Creator. Never mind that there is no empirical evidence at all that any of these unknown universes exists, let alone a thousand or a gazillion.

The conclusion that God exists doesn’t require faith. Atheism requires faith. It takes faith to believe in everything coming from nothing. It takes only reason to believe in everything coming from God.

I’m Peter Kreeft, professor of philosophy at Boston College, for Prager University.