The Will to Power · Friedrich Wilhelm Nietzsche
555.
The greatest of all fables is the one relating to knowledge. People would like to know how things-in-themselves are constituted: but behold, there are no things-in-themselves! But even supposing there _were_ an "in-itself," an unconditional thing, it could on that very account _not be known_! Something unconditioned cannot be known: otherwise it would not be unconditioned! Knowing, however, is always a process of "coming into relation with something"; the knowledge-seeker, on this principle, wants the thing, which he would know, to be nothing to him, and to be nothing to anybody at all: and from this there results a contradiction,--in the first place, between this _will_ to know, and this desire that the thing to be known _should_ be nothing to him (wherefore know at all then?); and secondly, because something which is nothing to anybody, does not even _exist,_ and therefore cannot be known. Knowing means: "to place one's self in relation with something," to feel one's self conditioned by something and one's self conditioning it under all circumstances, then, it is a process of _making stable or fixed,_ of _defining,_ of _making conditions conscious_ (not a process of _sounding_ things, creatures, or objects in-themselves).
Text from Project Gutenberg, public domain in the United States.