Johannes Buridanus: Summulae de Propositionibus (review)

John Buridan is now believed to be among the most influential later medieval philosophers, his philosophical analyses showing considerable acumen over a wide range of fields. His logical masterpiece, the lengthy Summulae de Dialectica (a commentary on a heavily modified version of Peter of Spain's thirteenth-century logic text, the Summulae Logicales) is composed of eight treatises, plus a treatise on sophismata, an important medieval genre of logical and semantic puzzles. It covers most of the major fourteenth-century logical topics, with their characteristic blend of traditional Aristotelian doctrine and terminist methods of propositional analysis.

The text of Buridan's Summulae was for many years only partially accessible in print, in an early printed edition (Venice 1499)—his commentary on the main text having been replaced by John Dorp's more concise commentary. In 1986, therefore, a group of European scholars launched the initiative of producing a modern critical edition of the entire Summulae, based upon the manuscripts. Since then, most of the treatises have been published, though at a rather slow pace: treatise 2 on predicables (ed. de Rijk, 1995), treatise 3 on categories (ed. Bos, 1994), treatise 4 on supposition (ed. van der Lecq, 1998), treatise 8 on demonstration (ed. de Rijk, 1999) and treatise 9 on the practice of sophisms (ed. Pironet, 2004) have been published, and now treatise 1 on propositions. Still in preparation are treatises 5 on syllogisms, 6 on topical reasoning, and 7 on fallacies.

The Summulae has recently appeared in an English translation by Gyula Klima (Yale University Press, 2001—prepared from pre-publication drafts of the critical text), but this fact in no way diminishes the significance of having this carefully-constructed modern edition of Buridan's De Propositionibus. Indeed, the importance of reliable editions of the writings of a philosopher of Buridan's stature hardly needs to be defended, given that serious scholarship requires the text to be consulted firsthand. Moreover, the volume includes an introduction with helpful information on editorial methods, as well as remarks on the project of editing the entire Summulae, and on the content of treatise 1 in particular. There is a comprehensive index of names and terms. Unlike the treatise on sophismata, which has attracted considerable interest since the 1950s (see Stephen Read's review of Pironet 2004 in this volume), this treatise has until now (unjustly) received little attention from scholars; but this will change with its appearance in a modern edition.

Treatise 1 on propositions corresponds, in Peter of Spain's Summulae, to a treatise called De Introductionibus, but Buridan rejected this title, making it clear that its main focus is propositions. It is composed of eight chapters, beginning with an interesting preface to the whole work, followed by two chapters on the nature of logic and its basic concepts.

It is only in the third chapter that the examination of propositions really begins: chapter 3 discusses propositions in general, including the division between categorical and hypothetical propositions; chapter 4 deals with opposition between categorical propositions, in particular the famous square of opposition; chapter 5 presents relations of equipollence (equivalence) between propositions; chapter 6 deals with the conversion of propositions, that is, relations of consequence that hold (or fail to hold) between propositions having the same terms, though in reverse order; chapter 7 deals with hypothetical propositions, which in medieval parlance included conditionals, conjunctions, and disjunctions (overlapping with some of the discussions in Buridan's Treatise on Consequences). Finally, in chapter 8, Buridan discusses modal propositions and their various logical properties.

One noteworthy aspect of this treatise is that it follows closely the contents of Aristotle's On Interpretation, except for the parts on hypothetical propositions (a notion absent from Aristotle's logic). But while chapters 1 through 7 are full of insightful analyses, it is in chapter 8 on modal propositions that one finds Buridan's most innovative contributions. By far the longest chapter of the treatise, it differs from the others in that Buridan does...