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Forum Philosophicum

Volume 14, Issue 1, Spring 2009

Petr Dvořák
Pages 87-99
DOI: 10.5840/forphil200914122

The Relational Logic of Franciscus Toletus and Petrus Fonseca

The well-known Ratio Studiorum of 1599 states that logical instruction should follow F. Toletus (Toledo) or P. Fonseca. The latter authored the famous Institutionum Dialecticarum Libri Octo (1564), the former a similar manual, Introductio in Dialecticam Aristotelis (1561). As is often observed, the contrast between the Aristotelian and present symbolic logics is perhaps most striking in their analysis of relational statements. Both authors recognize the relational logical form as independent from the traditional subject-predicate form and see the need to recognize relational inferential rules. They differ in their specific rules, however, so neither of the authors has captured the system of relational syllogism in its entirety.