  This willingness to take human language as it is found, with all of its ambiguities and rough edges, marks an important difference between Buridan and Ockham, the fourteenth-century philosopher with whom he is most often compared. Both make the traditional assumption that propositions, be they spoken, written, or mental, are the bearers of truth and falsity. Ockham, however, tends to see mental propositions as logically ideal or, in modern parlance,  ‘canonical’.[9]  The problem with spoken and written propositions is that because they depend on the meaning conventions of fallible users, they fail to be universal and logically perspicuous.  Thankfully, these shortcomings can be filtered out metalinguistically once we realize that the meanings of their constituent terms depend on their corresponding mental concepts, which naturally signify the same for everyone. So in Ockham's logic, the semantic relation between these concepts and what they signify outside the mind is of paramount importance; spoken and written terms have semantic properties too, of course, but in an entirely derivative way. By contrast, Buridan never privileges conceptual discourse or suggests that the logician might use it systematically to reform spoken or written language. He holds that spoken and written utterances—sometimes he uses the term ‘utterance [vox]’ where Ockham has ‘term [terminus]’—signify concepts primarily: “the capability of speaking was given to us in order that we could signify our concepts to others and also the capacity of hearing was given to us in order that the concepts of speakers could be signified to us” (S 4.1.2: 222). Accordingly, “utterances are imposed to signify things only through the mediation of the concepts by which those things are conceived” (QC 1: 4, ll. 45–6). Concepts are just the medium of signification for Buridan, the cognitive or psychological aspect of the signification of a word.