Third argument: why can we trust our reason?

Before we go on: two directions of thought

So far we have gone in one direction: from premises to a conclusion. But one can also think in the opposite direction. Clouds cause rain; that is the usual direction. But if I see that it is raining, I can conclude that there are clouds, even without lifting my head. That is the second direction: from what I already accept, to what it implies.

There is a well-known joke: “The philosopher starts from premises and arrives at conclusions. The theologian starts from the conclusions and looks for premises.” There is something true in it, and something entirely legitimate. Logically, “if A then B” is equivalent to “if not B, then not A.” If it rains there are clouds, and therefore if there are no clouds, it is not raining. Both directions are equally valid. The difference lies only in what I already know.

It is important to stress what this is not. It is not “believing because it is convenient.” An argument of the second kind does not choose premises because they are pleasant. It only reveals what I already believe in practice, without noticing. Incidentally, this is how science works too: from the falling of objects we infer that there is a force of gravity. That is exactly the second direction, from the facts to what explains them.

The next two arguments are of this kind, and that is precisely why they are especially strong. They do not tell you “believe.” They say: “Look at what you already believe, and at what it implies.”

Third argument: why can we trust our reason?

The American philosopher Richard Taylor proposed a parable. You are traveling by train and see on a hillside white stones arranged in the words “Welcome to Scotland.” In theory, it is possible that they rolled into that arrangement by chance over hundreds of years. But if you rely on the sign and say “I have arrived in Scotland,” you are already assuming that someone arranged them. You cannot both rely on the sign and think it came about by chance. That is a contradiction.

Our eyes and our reason are “the sign.” We rely on them to know the world, and in science even to understand it in depth, from tiny particles to galaxies. And now the second parable. Give a monkey a pile of television parts, and let it connect them however it likes. The chance that a working device will come out is almost zero. And if our brain was formed “by a monkey,” that is, by an entirely blind process, why, really, trust it? This is not skepticism for its own sake. It is a direct conclusion from the assumption that there is no God.

Notice what has happened here. In the previous argument, the atheist was forced to claim that complexity can arise by chance. Now he is caught in a vise: if so, his eyes and his reason also arose by chance, and he may not trust them. Not even his own arguments.

The wonder of the fit

This wonder is greater than it seems at first sight. How is our reason, born here on Earth, able to understand the universe at all? Great philosophers wrestled with this for centuries. David Hume showed that we do not learn the laws of nature from observation alone: we saw a few individual cases, and it is reason that generalizes a law from them. Immanuel Kant showed that we know things about the world through thinking too, and not only through the senses. But why should our thinking fit the world? The philosopher Hugo Bergmann, one of the founders of the Hebrew University, surveyed all the explanations proposed for this “miracle,” and found that all of them failed.

The wonder sharpens in mathematics. Mathematicians sometimes invent whole fields “in their heads,” with no connection to the world. And years later it turns out that they describe the laws of nature exactly. James Jeans, an important British physicist and astronomer of the early twentieth century, said of this: “The universe appears to have been designed by a mathematician.” And so too a principle that scientists use all the time: when there are several possible explanations, the simplest is usually the right one. When the car will not start, the mechanic checks the battery first, and does not assume three breakdowns that happened at once. And usually he is right. But why should the world “prefer” simple explanations? There is no explanation for this, unless someone built the world and reason so that they fit each other.

The answers

The first answer: “I do not claim that the senses are reliable. I only behave as if they were, because it works.” That is a possible escape, but a costly one. Whoever says this must admit that what he sees with his eyes is not knowledge either, but a “game” he plays. And above all, the answer does not explain the most important fact: that science succeeds. Planes fly, medicines heal, and predictions come true. If the senses and reason were only “as if,” why would it work?

The accepted answer: “Evolution selected good eyes, because they help survival.” It has several problems. The first is a circle: we discovered evolution with the help of our eyes and our reason. It cannot be used to prove that they can be trusted. It is like asking a person “can you be trusted?” and being convinced because he answered “yes.” Darwin himself relied on his eyes before he developed his theory, and people before Darwin relied on their eyes no less than we do.

And there is a further point here. Survival requires useful beliefs, not true beliefs. An animal that flees from every rustle, even when there is no predator there, will survive better than one that first checks whether it is true. In other words, evolution “selects” what helps survival, even when it is false. The second problem is the ant. To survive, one does not need to understand the universe. An ant understands nothing about its world, and yet it survives for millions of years, far longer than we have. Compared to the universe, our brain is not much bigger than its. And yet we understand the laws of galaxies and of tiny particles. Survival does not explain this.

The third problem: evolution is a random and gradual process, which never ends, and one cannot know where we are in it. And yet we rely on our eyes absolutely, as if we were the “pinnacle of creation,” and not a temporary product on the way to something else. When our eyes deceive us, as in a mirage in the desert, we see it as a malfunction that needs explaining. That itself shows how much we rely on them.

And in any case, even if evolution is true, perhaps God acts through it. This objection at most brings down the argument. It does not prove that there is no God.

The conclusion is surprising. Whoever relies on reason and on science already believes, without noticing, that someone intelligent built them so that they fit the world. It is commonly said that “where reason ends, faith begins.” It is exactly the reverse: reason itself rests on faith. A rational person must believe in an intelligent agent, and a consistent atheist must give up his trust in his own reason.