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." 515. The object is, not "to know," but to schematise,--to impose as much regularity and form upon chaos, as our practical needs require. In the formation of reason, logic, and the categories, it was a need in us that was the determining power: not the need "to know," but to classify, to schematise, for the purpose of intelligibility and calculation. (The adjustment and interpretation of all similar and equal things,--the same process, which every sensual impression undergoes, is the development of reason!) No pre-existing "idea" had anything to do with it: but utility, which teaches us that things can be reckoned with and managed, only when we view them roughly as equal.... _Finality_ in reason is an effect, not a cause: Life degenerates with every other form of reason, although constant attempts are being made to attain to those other forms of reason;--for Life would then become too obscure, too unequal. The categories are "truths" only in the sense that they are the conditions of our existence, just as Euclid's Space is a conditional "truth." (Between ourselves, as no one will maintain that men are absolutely necessary, reason, as well as Euclid's Space, are seen to be but an idiosyncrasy of one particular species of animals, one idiosyncrasy alone among many others....) The subjective constraint which prevents one from contradicting here, is a biological constraint: the instinct which makes us see the utility of concluding as we do conclude, is in our blood, we _are_ almost this instinct.... But what simplicity it is to attempt to derive from this fact that we possess an absolute truth! ... The inability to contradict anything is a proof of impotence but not of "truth." 516. We are not able to affirm and to deny one and the same thing: that is a principle of subjective experience--which is not in the least "necessary," _but only a sign of inability._