Origin of knowledge. – Through immense periods of time, the intellect produced nothing but errors; some of them turned out to be useful and species-preserving; those who hit upon or inherited them fought their fight for themselves and their progeny with greater luck. Such erroneous articles of faith, which were passed on by inheritance further and further, and finally almost became part of the basic endowment of the species, are for example: that there are enduring things; that there are identical things; that there are things, kinds of material, bodies; that a thing is what it appears to be; that our will is free; that what is good for me is also good in and for itself. Only very late did the deniers and doubters of such propositions emerge; only very late did truth emerge as the weakest form of knowledge. It seemed that one was unable to live with it; that our organism was geared for its opposite: all its higher functions, the perceptions of sense and generally every kind of sensation, worked with those basic errors that had been incorporated since time immemorial. Further, even in the realm of knowledge those propositions became the norms according to which one determined ‘true’ and ‘untrue’ – down to the most remote areas of pure logic. Thus the strength of knowledge lies not in its degree of truth, but in its age, its embeddedness, its character as a condition of life. Where life and knowledge seem to contradict each other, there was never any serious fight to begin with; denial and doubt were simply considered madness. Those exceptional thinkers, like the Eleatics, who still posited and clung to the opposites of the natural errors, believed in the possibility of also living this opposite: they invented the sage as the man of unchangeability, impersonality, universality of intuition, as one and all at the same time, with a special capacity for that inverted knowledge; they had the faith that their knowledge was at the same time the principle of life. But in order to be able to claim all this, they had to deceive themselves about their own state: they had fictitiously to attribute to themselves impersonality and duration without change; they had to misconstrue the nature of the knower, deny the force of impulses in knowledge, and generally conceive reason as a completely free, self-originated activity. They closed their eyes to the fact that they, too, had arrived at their propositions in opposition to what was considered valid or from a desire for tranquillity or sole possession or sovereignty. The subtler development of honesty and scepticism finally made also these people impossible; even their life and judgements proved dependent on the ancient drives and fundamental errors of all sentient existence. This subtler honesty and scepticism arose wherever two conflicting propositions seemed to be applicable to life because both were compatible with the basic errors, and thus where it was possible to argue about the greater or lesser degree of usefulness for life; also wherever new propositions showed themselves to be not directly useful, but at least also not harmful, as expressions of an intellectual play impulse, and innocent and happy like all play. Gradually the human brain filled itself with such judgements and convictions; and ferment, struggle, and lust for power developed in this tangle. Not only utility and delight, but also every kind of drive took part in the fight about the ‘truths’; the intellectual fight became an occupation, attraction, profession, duty, dignity – knowledge and the striving for the true finally took their place as a need among the other needs. Henceforth, not only faith and conviction, but also scrutiny, denial, suspicion, and contradiction were a power; all ‘evil’ instincts were subordinated to knowledge and put in its service and took on the lustre of the permitted, honoured, useful and finally the eye and the innocence of the good. Thus knowledge became a part of life and, as life, a continually growing power, until finally knowledge and the ancient basic errors struck against each other, both as life, both as power, both in the same person. The thinker – that is now the being in whom the drive to truth and those life-preserving errors are fighting their first battle, after the drive to truth has proven itself to be a life-preserving power, too. In relation to the significance of this battle, everything else is a matter of indifference: the ultimate question about the condition of life is posed here, and the first attempt is made here to answer the question through experiment. To what extent can truth stand to be incorporated? – that is the question; that is the experiment.