Until the launch of this series over fifteen years ago, the 15,000 volumes of the ancient Greek commentators on Aristotle, written mainly between 200 and 600 AD, constituted the largest corpus of extant Greek philosophical writings not translated into English or other European languages. Over 40 volumes have now appeared in the series, which is planned in some 80 volumes altogether. The last 14 chapters of book 1 of Aristotle's Prior Analytics are concerned with the representation in the formal language of syllogistic of propositions and arguments expressed in more or less everyday Greek. In his commentary on those chapters, Alexander of Aphrodisias explains some of Aristotle's more opaque assertions and discusses post-Aristotelian ideas in semantics and the philosophy of language. In doing so he provides an unusual insight into the way in which these disciplines developed in the Hellenistic era.