Abstract

Aristotle assesses as valid three first figure syllogisms, each of which contains at least one premiss expressing a de re contingency. In fact, all three of these moods (namely, Barbara-QQQ, Barbara-XQM, and Barbara-LQM) are invalid. Utilizing the concept of ampliation, this paper shows how the mood Barbara-QQQ must be refined if it is to be deemed valid. It can then become clear as to how Barbara-XQM and Barbara-LQM can be disambiguated and ultimately validated. In treating all three moods, some theses from S4 will be exploited in the context of distinguishing de dicto and de re modes of attributing possibility and necessity. Various Aristotelian propositional forms and rules of inference, including argumentation by ecthesis, will shape the presentation. The viability of Aristotle’s views on the convertibility of universal negative apodeictic propositions will emerge as decisive in evaluating the success of his modal syllogistic.