Qualities are our insurmountable barriers; we cannot possibly help feeling mere _differences of quantity_ as something fundamentally different from quantity--that is to say, as _qualities,_ which we can no longer reduce to terms of quantity. But everything in regard to which the word "knowledge" has any sense at all, belongs to the realm of reckoning, weighing, and measuring, to quantity whereas, conversely, all our valuations (that is to say, our sensations) belong precisely to the realm of qualities, _i.e._ to those truths which belong to us alone and to our point of view, and which absolutely cannot be "known." It is obvious that every one of us, different creatures, must feel different qualities, and must therefore live in a different world from the rest. Qualities are an idiosyncrasy proper to human nature; the demand that these our human interpretations and values, should be general and perhaps real values, belongs to the hereditary madnesses of human pride. 566. The "real world," in whatever form it has been conceived hitherto--was always the world of appearance _over again._ 567. The world of appearance, _i.e._ a world regarded in the light of values; ordered, selected according to values--that is to say, in this case, according to the standpoint of utility in regard to the preservation and the increase of power of a certain species of animals. It is _the point of view,_ then, which accounts for the character of "appearance." As if a world could remain over, when the point of view is cancelled! By such means _relativity_ would also be cancelled! Every centre of energy has its _point of view_ of the whole of the _remainder_ of the world--that is to say, its perfectly definite _valuation,_ its mode of action, its mode of resistance. The "world of appearance" is thus reduced to a specific kind of action on the world proceeding from a centre. But there is no other kind of action: and the "world" is only a word for the collective play of these actions. _Reality_ consists precisely in this particular action and reaction of every isolated factor against the whole. There no longer remains a shadow of a _right_ to speak here of "appearance." ... The _specific way of reacting_ is the only way of reacting; we do not know how many kinds and what sort of kinds there are. But there is no "_other,_" no "real," no essential being,--for thus a world _without_ action and reaction would be expressed.... The antithesis: world of appearance and real world, is thus reduced to the antitheses "world" and "nonentity." 568. A criticism of the concept "_real and apparent_ world."--Of these two the first is a mere fiction, formed out of a host of imaginary things. Appearance itself belongs to reality: it is a form of its being; _i.e._ in a world where there is no such thing as being, a certain calculable world of _identical_ cases must first be created through _appearance;_ a _tempo_ in which observation and comparison is possible, etc.