 Aquinas distinguishes between three principal stages of intellectual operation: first, the formation of concepts; second, the composition of judgments (propositions) built from concepts; third, inferential reasoning from one judgment to another. These last two stages were the subject of intensive study within medieval logic, but Aquinas has relatively little to say about logic, and is most interested in the initial stage of concept formation. Here, the possible intellect passively receives concepts that the agent intellect has abstracted from sensory impressions (phantasms). The possible intellect starts out as a blank slate, which is to say that Aquinas rejects the theory of innate ideas, at least as far as the possible intellect is concerned. Moreover, he is very clear that all our concepts arise from sensory experience: “the source of our cognition comes from the senses” (ST 1a 84.6sc). From this vantagepoint, he looks more like an empiricist than a rationalist. The role of agent intellect, however, complicates the situation. Whereas the possible intellect starts out as unformed potentiality, the agent intellect has the actuality to abstract universal concepts from sensory experience. It is not easy to say how abstraction occurs; indeed, for the whole of the Aristotelian tradition, the agent intellect has been something of a black box whose operation is taken as a brute fact rather than analyzed. Sometimes Aquinas suggests that the transformation of singular content into universal content occurs via the conversion of material phantasms into immaterial intelligible species, but the link between immateriality and universality is not entirely clear. (On abstraction see King 1994, Cory 2015).