_(d)_ Biology of the Instinct of Knowledge. Perspectivity. 493. _Truth is that kind of error_ without which a certain species of living being cannot exist. The value for _Life_ is ultimately decisive. 494. It is unlikely that our "knowledge" extends farther than is exactly necessary for our self-preservation. Morphology shows us how the senses and the nerves as well as the brain evolve in proportion as the difficulties of acquiring sustenance increase. 495. If the morality of "Thou shalt not lie" be refuted, the sense for truth will then have to justify itself before another tribunal--as a means to the preservation of man, _as Will to Power._ Likewise our love of the beautiful: it is also the _creative will._ Both senses stand side by side; the sense of truth is the means wherewith the power is appropriated to adjust things according to one's taste. The love of adjusting and reforming--a primeval love! We can only _take cognisance_ of a world which we ourselves have _made._ 496. Concerning the multifariousness of knowledge. The tracing of _its_ relation to many other things (or the relation of kind)--how should "knowledge" be of another? The way to know and to investigate is in itself among the conditions of life; that is why the conclusion that there could be no other kind of intellect (for ourselves) than the kind which serves the purpose of our preservation is an excessively hasty one: this _actual_ condition may be only an accidental, not in the least an essential; one. Our apparatus for acquiring knowledge is not adjusted for knowledge. 497. _The most strongly credited a priori "truths" are, to my mind, mere assumptions pending further investigation_; for instance, the law of causation is a belief so thoroughly acquired by practice and so completely assimilated, that to disbelieve in it would mean the ruin of our kind. But is it therefore true? What an extraordinary conclusion! As if truth were proved by the mere fact that man survives! 498. To what extent is our _intellect_ also a result of the conditions of life?--We should not have it did we not _need_ to have it, and we should not have it _as_ we have it, if we did not need it _as_ we need it--that is to say, if we could live otherwise. 499. Thinking in a primitive (inorganic) state is to _persevere in forms,_ as in the case of the crystal.--In _our_ thought, the _essential factor_ is the harmonising of the new material with the old schemes (= Procrustes' bed), the _assimilation_ of the unfamiliar. 500. The perception of the senses projected outwards: "inwards" and "outwards"--does the _body_ command here? The same equalising and ordering power which rules in the idioplasma, also rules in the incorporation of the outer world: our sensual perceptions are already the _result_ of this process of _adaptation_ and _harmonisation_ in regard to _all_ the past in us; they do not follow directly upon the "impression." 501.