Abstract

The present essay explores the sources and the scope of a major feature of the scholastic logic and metaphysics: the 16th-century distinction of the reasoningreason (distinctio rationis ratiocinantis) in contradistinction to the distinction of reasoned reason (distinctio rationis ratiocinatae). Depending on whether the nonidentity was meant to refer to first-order or second-order intentions, the distinctio rationis ratiocinantis intervened either between a definition and the term defined or between the two terms of identical propositions: »A = A«. How to save this elusive kind of distinction was a common concern of Thomists, Scotists and early modern Jesuits. Special attention is paid to the logician and metaphysician Bartholomew MASTRI (1602–73). German philosophy up to FREGE will be considered. Quite contrary to a time-honoured prejudice, the ancient metaphysics turns out to have been furnished with a powerful device in order to avoid the traps of reification.