 Insofar as [the primary concepts] are signified by expressions, and insofar as they are universals, and insofar as they are predicates or subjects, and insofar as they are defined in terms of each other, and insofar as they are asked about and taken in a question about them, they are logical. They are taken so as to investigate the compounds of them, one with another, where the aforementioned things attach to them, and the features of the compounds after they have been compounded. ([Letters] (12)  67.1–5).[11] 