Abstract

This thesis investigates for the first time the logical writings of the fourteenth-century philosopher, R. Levi ben Gershom . Gersonides wrote a super-commentary on Averroes' Middle Commentary on the Organon, a commentary on two of Averroes' logical questions, and an independent treatise, The Book of the Correct Syllogism. To say that these writings have been completely neglected would not be quite accurate. Parts of the supercommentary were translated into Latin in the sixteenth century and printed with the works of Aristotle and Averroes; in this format they attracted the attention of Prantl and others. But while the translated works were the most popular of Gersonides' logical writings at that time, they are not the most noteworthy nor the most interesting to modern historians of logic. Hence, it has been necessary to make a review of the writings in manuscript in an attempt to isolate the topics which are likely to be representative and of importance in the development of medieval logic. ;Following an introductory chapter on Gersonides' logical writings, the second chapter deals with Gersonides' conception of logic. Special attention is given to the question of the domain of logic, and specifically, to the claim that logic investigates, in addition to language and thought, real existing things. Chapter three analyzes Gersonides' program of deriving the valid syllogistic moods from rules that yield "consequences on account of the part and the whole" and closes with his defence of the fourth syllogistic figure. ;The next three chapters consider Gersonides' modal logic. Chapter four is devoted to his critique of Aristotle's treatment of modal syllogistic as interpreted by Averroes. It is suggested that some of the criticisms are reminiscent of points made in recent studies of Aristotle's modal logic. In chapters five and six, Gersonides' own modal logic is considered. ;Part two presents a partial edition and translation of Gersonides' Book of the Correct Syllogism. It is argued that Gersonides revised the Correct Syllogism in light of new materials on modal logic which came into his hands after he had written the first edition