You "ought" to believe in God

Moral considerations prove the existence of God--or at least oblige us to believe in it, according to the great German philosopher Immanuel Kant (1724-1804).

Kant actually rejects Anselm’s and Descartes’s arguments for the existence of God, but that needn’t mean he rejects theism itself. Indeed he goes on to offer his own rather original argument to that end; although there may be hints of the strategy in Aquinas and others, Kant is the first explicitly to use moral considerations to prove God’s existence. Or perhaps more precisely, morality does not so much “prove” God’s existence as oblige us to believe in it.

Moral agents, it seems clear, ought to promote the realization of the highest good. For surely we would not be acting rightly if we sought to bring about less than the highest good! But “ought implies can,” as philosophers like to say: one cannot say that someone “ought” to do a particular action unless that action is actually possible for them. For example, we would not say of you that you were morally obliged to end world hunger, for that isn’t even remotely possible for you. At most we might say you were obliged to make small steps in that direction, such as giving to charities.

But if we ought to promote the realization of the highest good and if ought implies can, it follows that it must be possible for us to promote the realization of the highest good.

But now the highest good has two components. The first is moral virtue, and this is entirely in our power. But the second is this: the world would not in fact manifest the highest good unless its moral agents were also happy, and happy in strict proportion to their virtue. To be sure, it is not to become happy that we act morally: morality is a matter of doing what is right for its own sake, not in order to promote our happiness. But imagine a world where the virtuous people suffered grossly and the evil people prospered! Clearly something would be wrong about such a world. Just as clearly, therefore, the highest good for the world would be one where one’s happiness is proportional to one’s virtue.

But we ourselves do not directly control most of what goes on in the world. We do not have power over the laws of nature, for example. There is therefore nothing in our power to ensure that happiness be distributed in proportion to virtue. And indeed just looking around it may seem very questionable that happiness in fact is so distributed. But for that even to be possible, to be something it is reasonable to hope for in the long run, it’s clear we need to believe in a being who could bring it about: a being who obviously must be supremely good and powerful and in charge of the causal structure of the world.

For the highest good even to be possible, in short, God must exist. And it is possible: we are obliged to promote it as we saw, and could not be so obliged unless it were possible.

It follows, Kant concludes, that God exists.

Or at least we must believe it to be so. For we are obliged to aim for the highest good and we would be incapable of aiming for that unless we believed that it was possible. Putting it this way may not quite prove that God in fact exists. But it would make belief in God morally necessary for us: something we must believe as strongly as we believe in morality in the first place.


Sources:
(1) Immanuel Kant, Critique of Practical Reason. Transl. Lewis W. Beck (New York, NY: Macmillan Publishing Company, 1985/1956), 128-136.
(2) Immanuel Kant, Religion Within the Limits of Reason Alone. Transl. T. M. Greene and H. H. Hudson (New York, NY: Harper, 1960), 4-7.