Architectural theory arises from building, when the mind considers its symbolic relations to its own constructions. The intent of this essay is to discuss the intellectual causes that precede building and precede theory. It considers certain fundamental dualities in our thinking about architecture—such as image and word; type and model; imitation and invention—and the role they play in its making, its perfection as an art, and the eventual elaboration of its tenets into a theory. At a time when theories of architecture proliferate as expressions of ‘personal philosophies,’ a careful and incisive philosophical approach to if, how, and when does theory become formative of building, may ensure that architecture remain faithful to its intrinsic purposes.