What’s the what

“Concepts are functions of the mind, i.e., of individual minds. They may be derived from and signify perceptions of things in the field of space and time; or they may derive from and signify acts of the mind, the minds of thinking individuals; but in no case can they signify entities other than those in the mind or those perceived. The concept ‘dog,’ for example, is in the mind and signifies certain perceptions of creatures of a certain alikeness outside. It cannot be assumed to signify some metaphysical quidditas, whatness, or general substance dog, as an idea in a ‘divine’ mind somewhere else, of which all the living and dead individuals classified by analogy as ‘dog’ are representations.” – Joseph Campbell, The Masks of God: Occidental Mythology