An interesting and certainly inevitable outcome of Nietzsche's argument appears in Aph. 516, where he declares that even our inability to deny and affirm one and the same thing is not in the least necessary, but only a sign of inability.
The whole argument of Part I. tends to draw science ever nearer and nearer to art (except, of course, in those cases in which science happens to consist merely of an ascertainment of facts), and to prove that the one like the other is no more than a means of gaining some foothold upon the slippery soil of a world that is for ever in flux.
In the rush and pell-mell of Becoming, some milestones must be fixed for the purposes of human orientation. In the torrent of evolutionary changes pillars must be made to stand, to which man can for a space hold tight and collect his senses. Science, like art, accomplishes this for us, and it is our will to power which "creates the impression of Being out of Becoming" (Aph. 517).
According to this standpoint, then, consciousness is also but a weapon in the service of the will to power, and it extends or contracts according to our needs (Aph. 524). It might disappear altogether (Aph. 523), or, on the other hand, it might increase and make our life more complicated than it already is. But we should guard against making it the Absolute behind Becoming, simply because it happens to be the highest and most recent evolutionary form (Aph. 709). If we had done this with each newly acquired characteristic, sight itself, which is a relatively recent development, would also have required to have been deified.
Pantheism, Theism, Unitarianism—in fact all religions in which a conscious god is worshipped, are thus aptly classed by Nietzsche as the result of man's desire to elevate that which is but a new and wonderful instrument of his will to power, to the chief place in the imaginary world beyond (eternal soul), and to make it even the deity itself (God Omniscient).
With the question of Truth we find Nietzsche quite as ready to uphold his thesis as with all other questions. He frankly declares that "the criterion of truth lies in the enhancement of the feeling of power" (Aph. 534), and thus stands in diametrical opposition to Spencer, who makes constraint or inability the criterion of truth. (See Principles of Psychology, new edition, chapter ix.... "the unconceivableness of its negation is the ultimate test of the truth of a proposition.")
However paradoxical Nietzsche's view may seem, we shall find that it is actually substantiated by experience; for the activity of our senses certainly convinces us more or less according to the degree to which it is provoked. Thus, if we walked for long round a completely dark room, and everything yielded, however slightly, to our touch, we should remain quite unconvinced that we were in a room at all, more particularly if—to suppose a still more impossible case—the floor yielded too. What provokes great activity in the bulbs of our fingers, then, likewise generates the sensation of truth.
From this Nietzsche proceeds to argue that what provokes the strongest sentiments in ourselves is also true to us, and, from the standpoint of thought, "that which gives thought the greatest sensation of strength" (Aph. 533).
The provocation of intense emotion, and therefore the provocation of that state in which the body is above the normal in power, thus becomes the index to truth; and it is a very remarkable thing that two prominent English thinkers should, at the very end of their careers, have practically admitted this, despite the fact that all their philosophical productions had been based upon a completely different belief. I refer, of course, to Spencer and Buckle, who both upheld the view that in a system of thought the emotional factor is of the highest importance.
It follows from all this, that lies and false doctrines may quite conceivably prove to be even more preservative to species than truth itself, and although this is a view we have already encountered in the opening aphorisms of Beyond Good and Evil, in Aph, 538 this volume we find it further elucidated by Nietzsche's useful demonstration of the fact that "the easier way of thinking always triumphs over the more difficult way"; and that logic, inasmuch as it facilitated classification and orderly thought, ultimately "got to act like truths."