Read it through once

It is an axiom in mental philosophy, that we can think of nothing which we have not perceived. When I say that we can think of nothing, I mean, we can imagine nothing, we can reason of nothing, we can remember nothing, we can foresee nothing. The most astonishing combinations of poetry, the subtlest deductions of logic and mathematics, are no other than combinations which the intellect makes of sensations according to its own laws. A catalogue of all the thoughts of the mind, and of all their possible modifications, is a cyclopedic history of the universe.