 One idea that has been used in such characterizations, and that is also present in Aristotle, is that logical expressions do not, strictly speaking, signify anything; or, that they do not signify anything in the way that substantives, adjectives and verbs signify something. “Logic [dialektike] is not a science of determined things, or of any one genus” (Posterior Analytics, 77a32–3). We saw that the idea was still present in Kant and the early Wittgenstein. It reemerged in the Middle Ages. The main sense of the word “syncategorematic” as applied to expressions was roughly this semantic sense (see Kretzmann 1982, pp. 212 ff.). Buridan and other late medieval logicians proposed that categorematic expressions constitute the “matter” of sentences while the syncategorematic expressions constitute their “form” (see the text quoted by Bocheński 1956, §26.11). (In a somewhat different, earlier, grammatical sense of the word, syncategorematic expressions were said to be those that cannot be used as subjects or predicates in categorical propositions; see Kretzmann 1982, pp. 211–2.) The idea of syncategorematicity is somewhat imprecise, but there are serious doubts that it can serve to characterize the idea of a logical expression, whatever this may be. Most prepositions and adverbs are presumably syncategorematic, but they are also presumably non-logical expressions. Conversely, predicates such as “are identical”, “is identical with itself”, “is both identical and not identical with itself”, etc., which are resolutely treated as logical in recent logic, are presumably categorematic. (They are of course categorematic in the grammatical sense, in which prepositions and adverbs are equally clearly syncategorematic.)