THE CATEGORICAL IMPERATIVE.—Thus, at least, thought Kant, and he said: There is a practical reason which does not go beyond experience and does not seek to go beyond it; but which does not depend on it, is absolutely separated from it, and is its own (human) experience by itself. This practical reason says to us: you ought to do good. The crowd call it conscience; I call it in a general way practical reason, and I call it the categorical imperative when I take it in its principle, without taking into account the applications which I foresee. Why this name? To distinguish it clearly; for we feel ourselves commanded by other things than it, but not in the same way. We feel ourselves commanded by prudence, for instance, which tells us: do not run down that staircase if you do not wish to break your neck; we feel ourselves commanded by the conventions which say: be polite if you do not wish men to leave you severely alone, etc. But conscience does not say if to us: it says bluntly "you ought" without consideration of what may or may not happen, and it is even part of its character to scorn all consideration of consequences. It would tell us: run down that staircase to save that child even at the risk of breaking your neck. Because of that I call all the other commandments made to us hypothetical imperatives and that of conscience, alone, the categorical or absolute imperative. Here is a definite result.
MORALITY, THE LAW OF MAN.—Yet reflect: if the foregoing be true, morality is the very law of man, his especial law, as the law of the tree is to spread in roots and branches. Well. But for man to be able to obey his law he must be free, must be able to do what he wishes. That is certain. Then it must be believed that we are free, for were we not, we could not obey our law; and the moral law would be absurd. The moral law is the sign that we are free. Compared to this, all the other proofs of freedom are worthless or weak. We are free because we must be so in order to do the good which our law commands us to do.
Let us examine further. I do what is right in order to obey the law; but, when I have done it, I have the idea that it would be unjust that I should be punished for it, or that I should not be rewarded for it, that it would be unjust were there not concordance between right and happiness. As it happens, virtue is seldom rewarded in this world and often is even punished; it draws misfortune or evil on him who practises it. Would not that be the sign that there are two worlds of which we see only one? Would not that be the sign that virtue unrewarded here will be rewarded elsewhere in order that there should not be injustice? It is highly probable that this is so.
But for that it is necessary that the soul be immortal. It is so, since it is necessary that it should be. The moral law is accomplished and consummated in rewards or penalties beyond the grave, which pre-suppose the immortality of the soul. All the other proofs of the immortality of the soul are worthless or feeble beside this one which demonstrates that were there no immortality of the soul there would be no morality.
GOD.—And, finally, if justice is one day to be done, this supposes a Judge. It is neither ourselves who in another life will do justice to ourselves nor yet some force of circumstances which will do it to us. It is necessary to have an intelligence conceiving justice and a will to realise it. God is this intelligence and this will.
All the other proofs of God are weak or worthless beside this one. The existence of God has been deduced from the idea of God: if we have the idea of God, it is necessary that He should exist. A weak proof, for we can have an idea which does not correspond with an object. The existence of God has been deduced from the idea of causality; for all that is, a cause is necessary, this cause is God. A weak proof, for things being as they are, there is necessity for ... cause; but a cause and a single cause, why? There could be a series of causes to infinity and thus the cause of the world could be the world itself. The existence of God has been deduced from the idea of design well carried out. The composition, the ordering of this world is admired; this world is well made; it is like a clock. The clock supposes a clock-maker; the fine composition of the world supposes an intelligence which conceived a work to be made and which made it. Perhaps; but this consideration only leads to the idea of a manipulation of matter, of a demiurge, as the Greeks said, of an architect, but not to the idea of a Creator; it may even lead only to the idea of several architects and the Greeks perfectly possessed the idea of a fine artistic order existing in the world when they believed in a great number of deities. This proof also is therefore weak, although Kant always treats it with respect.
The sole convincing proof is the existence of the moral law in the heart of man. For the moral law to be accomplished, for it not to be merely a tyrant over man, for it to be realised in all its fullness, weighing on man here but rewarding him infinitely elsewhere, which means there is justice in all that, it is necessary that somewhere there should be an absolute realizer of justice. God must exist for the world to be moral.
Why is it necessary for the world to be moral? Because an immoral world with even a single moral being in it would be a very strange thing.
Thus, whilst the majority of philosophers deduced human liberty from God, and the spirituality of the soul from human liberty, the immortality of the soul from human spirituality, and morality from human immortality, Kant starts from morality as from the incontestable fact, and from morality deduces liberty, and from liberty spirituality, and God from the immortality of the soul with the consequent realization of justice.
He has effected an extraordinarily powerful reversal of the argument generally employed.