  First, Buridan did much to streamline and better articulate the methods of terminist logic. The most important analytical tool in the Summulae is the doctrine of suppositio [supposition], which had been a feature of terminist logic for several generations by the time Buridan arrived in Paris. Terms were thought to possess two general semantic properties: signification, or what a term ‘makes known’ in the mind of the person who sees it or hears it or conceives of it, whether mediately or immediately (thus, the written term ‘Socrates’ brings to mind the concept of Socrates, which in turn signifies the actual person); and supposition, which refers to the capacity of certain substantive terms to stand for or ‘pick out’ something in a particular context, such as in a proposition. Although the analogy is not perfect, supposition performs many of the same functions as what we would call the theory of  reference.[15]  Traditional accounts divided supposition into proper supposition, where a term is used with its typical or standard meaning, and improper supposition, where a term is used in some metaphorical or figurative sense. Most logicians went on to distinguish three kinds of proper supposition: personal, where a term stands for what it signifies (e.g., ‘Socrates’ in ‘Socrates is a man’); material, where it stands for itself (e.g., ‘man’ in ‘Man has three letters’); and simple, where it stands for a common nature or concept (e.g., ‘man’ in ‘Man is a species’). Simple supposition appears to have been a vestige of early terminist  logic,[16]  whose realist practitioners needed to distinguish between referring to a universal thing and referring to a particular thing. But by the fourteenth century, the whole notion of universals had become more controversial, and nominalist logicians in particular were not about to accept any special device for referring to them through common terms such as ‘man’. So simple supposition was readapted to model reference to common concepts or intentions. Thus, Ockham holds that a term exhibits simple supposition when it supposits “for a concept in the mind [pro conceptu mentis],” and is not being used  significatively.[17]  What united Ockham and his terminist predecessors was their realization that if the proposition ‘Man is a species’ is to be true, then the term ‘man’ cannot supposit personally for any of the individual men it ultimately signifies, since it cannot be said of any of them that he is a species (Socrates is a man, not a species).  Accordingly, the reference of ‘man’ must be to a common nature or concept.