everything is in a ceaseless flux, says Heraclitus; there is no permanent being; all is change and becoming. It must be left to metaphysical speculation to deal with the problems whether this proposition can be borne out from the point of view of a superhuman intelligence and furthermore whether it is possible for a human mind to think of change without implying the concept of a substratum that, while it changes, remains in some regard and sense constant in the succession of its various states. For epistemology, the theory of human knowledge, there is certainly something that it cannot help considering as permanent, viz., the logical and praxeological structure of the human mind, on the one hand, and the power of the human senses, on the other hand. Fully aware of the fact that human nature as it is in this epoch of cosmic changes in which we are living is neither something that existed from the very beginning of all things nor something that will remain forever, epistemology must look upon it as if it were unchanging. The natural sciences may try to go further and to study the problems of evolution. But epistemology is a branch—or rather, the basis—of the sciences of man. It deals with one aspect of the nature of man as he emerged from the aeons of cosmic becoming and as he is in this period of the history of the universe. It does not deal with thinking, perceiving and knowing in general, but with human thinking, perceiving and knowing. For epistemology there is something that it must take as unchanging, viz., the logical and praxeological structure of the human mind.
One must not confuse knowledge with mysticism. The mystic may say that "shadow and sunlight are the same." Knowledge starts from the clear distinction between A and non-A.
We know that there were ages of cosmic history in which there did not exist beings of the kind we call Homo sapiens, and we are free to assume that there will be again ages in which this species will not exist. But it is vain for us to speculate about the conditions of beings that are, in the logical and praxeological structure of their minds and in the power of their senses, essentially different from man as we know him and as we are ourselves. Nietzsche's concept of a superman is devoid of any epistemological meaning.