Dialectical Reasoning and Topical Argument in the Middle Ages: an Inquiry into the Commentaries on Aristotle's Topics (1250-1500)

In my dissertation I have analysed 35 commentaries on the Topics from various epochs and places. I have focused my attention on the possible influences of the different views about logic and logical doctrines on the different approaches to the Topics that Medieval commentators employed. The main outcome of this scrutiny was the identification of two different and autonomous exegetical traditions, namely British, and continental or Parisian.

Furthermore, my research has highlighted the presence of the Boethian tradition of the topics alongside its Aristotelian counterpart. The presence of the Boethian topics was attested to by the demarcation between the logical and epistemological facets of dialectical reasoning. This demarcation was expressed through the distinction proposed by Parisian ‘pluralists’ between inferring and proving syllogisms, or through the Buridanian separation between the illatio and the probatio. Both the Parisian ‘pluralists’ and John Buridan and his followers described the probative side of reasoning in connection to the Boethian definition of argument. Thus, they characterized the proving argumentum in terms of cognitive psychology. The proving argument did not consist in the mere correct application of logical rules of inference, which yielded a necessary conclusion, but it was a reasoning that engendered a belief in the subject. And the topic, especially the locus maxima propositio, was the warrant for the transfer of belief from the premises, which were more known and believed than the doubted conclusion, to the conclusion itself. Thus, in commentaries written by Parisian ‘pluralists’, Buridan and his followers, the dialectical reasoning was not limited to the dialectical syllogism, which differed from the other types of syllogisms only in virtue of the epistemic state of its premises. For these authors influenced by Boethius, the dialectical reasoning was a topical reasoning, which differed from the formal reasoning since it started from different points, applied diverse rules, and produced different results. This ‘epistemological’ understanding of the dialectical reasoning allowed commentators to enlarge the spectrum of dialectical reasoning and to expand upon less rigorous kinds of argumentations, namely induction, enthymeme and example.