ABSTRACT
Jean Buridan clearly distinguishes between necessity-propositions and propositions that are necessary, and similarly for the other modes. Buridan, like William Ockham and Pierre Abelard before him, draws a distinction between compound and divided modals, but there are important differences in the ways these three logicians draw the distinction. For Buridan, whether a proposition is compound or divided depends on what its subject and predicate are. Hughes uses the phrase 'the octagon of opposition' to describe the diagram in Buridan that records the logical relations between quantified modal propositions. Buridan considers the Aristotelian rule that nothing impossible follows from an assertoric proposition put forward as possible. Like Ockham, Buridan explores a number of alternatives to his principal system. These include systems in which the ampliation of modals is cancelled by prefixing the words 'that is' to the subject, or modals are read in the compound sense.
