PRACTICAL REASON.--_But_ there is perhaps another reason, or another aspect of reason--to wit, practical reason. What is practical reason? Something in us tells us: you should act, and you should act in such a way; you should act rightly; this is not right, so do not do it; that is right, do it. As a fact this is uncontestable. What is the explanation? From what data of experience, from what systematization of the understanding has our mind borrowed this? Where has it got it? Does nature yield obedience to a "you ought"? Not at all. It exists, and it develops and it goes its way, according to our way of seeing it in time and space, and that is all. Does the understanding furnish the idea of "you ought"? By no means; it gives us ideas of quantity, of quality, of cause and effect, etc., and that is all; there is no "you ought" in all that. Therefore this "you ought" is purely human; it is the only principle which comes exactly from ourselves only. It might therefore well be the very foundation of us.--It may be an illusion.--No doubt, but it is highly remarkable that it exists, though nothing gives it birth or is of a nature to give it birth. An illusion is a weakness of the senses or an error of logic and is thus explained; but an illusion in itself and by itself and only proceeding from itself is most singular and not to be explained as an illusion. Hence it remains that it is a reality, a reality of our nature, and given the coercive force of its voice and act, it is the most real reality there is in us. 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.