507 (Spring-Fall 1887)--Nietzsche, WtP
The valuation "I believe that this and that is so" as the essence of "truth." In valuations are expressed conditions of preservation and growth. All our organs of knowledge and our senses are developed only with regard to conditions of preservation and growth. Trust in reason and its categories, in dialectic, therefore the valuation of logic, proves only their usefulness for life, proved by experience--not that something is true.
That a great deal of belief must be present; that judgments may be ventured; that doubt concerning all essential values is lacking--that is the precondition of every living thing and its life. Therefore, what is needed is that something must be held to be true--not that something is true.
"The real and the apparent world"--I have traced this antithesis back to value relations. We have projected the conditions of our preservation as predicates of being in general. Because we have to be stable in our beliefs if we are to prosper, we have made the "real" world a world not of change and becoming, but one of being.