The falseness of an opinion is not for us any objection to it: it is here, perhaps, that our new language sounds most strangely. The question is, how far an opinion is life-furthering, life- preserving, species-preserving, perhaps species-rearing, and we are fundamentally inclined to maintain that the falsest opinions (to which the synthetic judgments a priori belong), are the most indispensable to us, that without a recognition of logical fictions, without a comparison of reality with the purely IMAGINED world of the absolute and immutable, without a constant counterfeiting of the world by means of numbers, man could not live—that the renunciation of false opinions would be a renunciation of life, a negation of life. TO RECOGNISE UNTRUTH AS A CONDITION OF LIFE; that is certainly to impugn the traditional ideas of value in a dangerous manner, and a philosophy which ventures to do so, has thereby alone placed itself beyond good and evil.

— Beyond Good and Evil by Friedrich Nietzsche
Chapter I. On the Prejudices of Philosophers

(Source: en.wikisource.org)