Summulae de Locis Dialecticis by Johannes Buridanus (review)

The fourteenth-century logician John Buridan was without a doubt one of the sharpest, most gifted among Latin medieval logicians. Treatise 6 of his gigantic logical compendium Summulae de Dialectica (English translation by Gyula Klima, Yale University Press, 2000, made on the basis of a preliminary Latin edition by Hubert Hubien) is on dialectical loci. This is the text that has just been critically edited by Niels Jørgen Green-Pedersen as part of the ongoing collective effort to produce critical editions of all the treatises of Buridan’s Summulae; only the treatise on fallacies remains. Given the extraordinary importance of his logical works, not only in terms of theoretical sophistication but also in terms of how widely read they were, one cannot overestimate the importance of these critical editions of the different treatises in the Summulae for the students and scholars of Latin medieval logic.

To appreciate the importance of this publication, some context is in order. Among the six logical works by Aristotle, two in particular deal specifically with arguments and their structures: the Prior Analytics and the Topics. One could add to the list the Sophistical Refutations, which is about arguments that appear correct but are not. The Prior Analytics presents a rigorously defined logical system, syllogistic, which is able to determine exactly when an argument is valid or not, but only for arguments fitting the “mold” defined by the theory: arguments composed of categorical sentences, having two premises and one conclusion. In this sense, the scope of action of syllogistic is rather limited. In the long tradition of Aristotelian logic, the large surplus of arguments one might be interested in, but which do not fit the syllogistic mold, was often treated instead from the point of view of the framework presented in the Topics.

Aristotle’s Topics is above all a work on dialectic, that is, the oral disputations that occupied such a prominent role in ancient Greek philosophy. Especially Books I and VIII focus on the rules and principles for such dialectical exchanges. Books II to VII in turn present what became known among Latin medieval authors as the ‘doctrine of the loci,’ that is, argumentation schemata that can be used to produce, evaluate or justify valid arguments (see chapter 2, Handbook of Argumentation Theory, Springer, 2015). The doctrine of the loci is not nearly as systematic and rigorous as syllogistic, but it represents an important complement to the latter in virtue of its broader scope.

As is well known, in the first instance Boethius was the sole transmitter of Aristotelian logic to the Latin medieval tradition. His textbooks on syllogistic as well as his treatise on topical differentiae were widely read; in the latter, Boethius focuses on the doctrine of the loci presented in Books II to VII of the Topics, which thus became a stock item in the Latin medieval logical tradition. Most if not all major authors of the period composed treatises or chapters on the topic, and more often than not under the influence of Boethius. Buridan is no exception to the rule.

By the time Buridan was writing the Summulae, the doctrine of loci was already losing some of its relevance in virtue of the development of theories of consequence (see Catarina Dutilh Novaes, “Medieval Theories of Consequence,” Stanford Encyclopedia of Philosophy, 2012), which generalized and unified both the theory of syllogistic and the doctrine of the loci. But it remained an important topic in the logical curriculum, as evidenced by the fact that Buridan includes a whole treatise on it in his Summulae. Buridan does not seem to introduce great novelties into the general content of doctrines of the loci, but with his characteristic sharpness, produces what is perhaps “the most precise and most interesting exposition of the doctrine of the loci in the medieval logical literature,” as Green-Pedersen rightly comments.

The volume is prepared with the usual care and competence of all volumes...