Nature does nothing in vain, and in the use of means to her goals she is not prodigal. Her giving to man reason and the freedom of the will which dep… - Immanuel Kant

Man, and in general every rational being, exists as an end in himself, not merely as a means for arbitrary use by this or that will: he must in all his actions, whether they are directed to himself or to other rational beings, always be viewed at the same time as an end.

Man has his own inclinations and a natural will which, in his actions, by means of his free choice, he follows and directs. There can be nothing more dreadful than that the actions of one man should be subject to the will of another; hence no abhorrence can be more natural than that which a man has for slavery. And it is for this reason that a child cries and becomes embittered when he must do what others wish, when no one has taken the trouble to make it agreeable to him. He wants to be a man soon, so that he can do as he himself likes.

To know what questions may reasonably be asked is already a great and necessary proof of sagacity and insight. For if a question is absurd in itself and calls for unnecessary answers, it not only brings disgrace to the person raising it, but may prompt an incautious listener to give absurd answers, thus presenting, as the ancients said, the laughable spectacle of one person milking a he-goat, and another holding the sieve underneath.