  With William of Ockham (ca. 1285–1347/49), however, the concepts of sign and signification begin to take center stage in logic (Biard 1981, 452; Biard 1989, Lenz 2003, Panaccio 2004). Logic is seen as exclusively concerned with signs, primarily with mental signs, secondarily with vocal or written signs.  Ockham integrates the concept of supposition into his definition of sign. He recognizes that the general notion of sign as something that makes something else come into cognition is too broad to be useful in logic and semantic theory; therefore, he adds to the definition the criterion that a sign, as far as its use in logic is concerned, has to be apt to stand for the thing it makes come into cognition, or else it has to be such that it could be added to such a sign standing for something (natum est pro illo supponere vel tali addi in propositione) (William of Ockham, Summa log., 1974, 9).[45] Thus, Ockham's logical concept of sign is restricted to what later will be termed a ‘propositional sign’ (signum propositionale) (John Raulin, In log. Arist. comment., 1500, fol. a5rb). Due to the central position of the notion of sign in his logic, one is entitled to characterize Ockham's logic as “ruled by the concept of sign” (“régie par le concept de signe”) (Biard 1989, 102). Ockham, constantly referring to the notion of sign, ventures in many cases a semiological redefinition of basic logical concepts (Biard 1989, 102–25), which in turn allows him to reformulate traditional ontological issues, as for instance the questions of universals, the number of categories, or the ontological status of relations, as semantic questions.