“[T]he understanding … has its essence in itself, consequently it has nothing, together with or external to itself, which can be ranged beside it; it is incapable of being compared, because it is itself the source of all combinations and comparisons; … we measure all things by understanding alone; … it is … the principle of all generalising, of all classification, … [I]t circumscribes all things and beings. The definitions which the speculative philosophers and theologians give … , all these definitions are … ideas drawn solely from the nature of the understanding.”