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188 him continually relapsing into the ordinary methods of speech. He says time and again that the necessities of life prove nothing as to truth. Schematizing for purposes of practical control he still specifically distinguishes from knowing. Is it really knowing a thing, he asks, to class it with something else with which one is already familiar and so find it less strange?—this when both alike may be unknown, the things we are most familiar with being sometimes the least known, inasmuch as they excite no curiosity and we fancy we know them already. Comprehending, explaining, understanding—that alone fills out Nietzsche's idea of knowing; and classifying, not to say mathematizing, only touches the borders of the subject. undefined That a belief is convenient, practical, even necessary, proves nothing as to its standing in foro scientiæ. The law of causality, for example, may, like other so-called a priori truths, be so much a part of us that unbelief in it would cause our undoing—is it therefore true? As if truth were proved by our remaining alive! The idea of an "ego" may be indispensable, and for all that be a fiction. The ideas of a given type of being simply prove what is necessary for it, and the ideas may vary as the types vary. The Euclidean space may, like our kind of reason, be simply an idiosyncrasy of certain kinds of animals—other kinds might find necessary a space of four dimensions and have a different type of logic from the human. So with valuations. The valuations of one species, being from the standpoint of its particular interests, may differ from those of another species, the interests of which are different; or, if the ruling impulses vary, differing estimations of ends and means, different interpretations of historical events, different world-perspectives generally may result. undefined It is naïve to take man as the measure of things, either theoretically or practically. We do not know