The Will to Power · Friedrich Wilhelm Nietzsche
514.
A moral--that is to say, a method of living which long experience and experiment have tested and proved efficient, at last enters consciousness as a law, as dominant.... And then the whole group of related values and conditions become part of it: it becomes venerable, unassailable, holy, true; a necessary part of its evolution is that its origin should be forgotten.... That is a sign that it has become master. Exactly the same thing might have happened with the categories of reason: the latter, after much groping and many trials, might have proved true through relative usefulness.... A stage was reached when they were grasped as a whole, and when they appealed to consciousness as a whole,--when belief in them was commanded,--that is to say, when they acted as if they commanded.... From that time forward they passed as a priori, as beyond experience, as irrefutable. And, possibly, they may have been the expression of no more than a certain practicality answering the ends of a race and a species,--their usefulness alone is their "truth."
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