23. Marsilius of Inghen on the Principle of Non-Contradiction

The principle of non-contradiction is one of the most discussed subjects in the history of philosophy. Philosophers and theologians of the fourteenth century showed great interest in it. It was qualified as a primum principium or ‘first principle’. They posed many questions: How should it be formulated? What is its ontological status? They discussed these problems primarily in their commentaries on Aristotle’s Metaphysics . This chapter discusses questions of this kind as they are found in commentaries by the theologian and philosopher Marsilius of Inghen. He is interesting, first because both he and his master, the philosopher John Buridan (ca. 1298–ca. 1360), challenge Aristotelian schemes of the relation between substance and accident with the help of this principle; second, because Marsilius challenges even the principle itself in virtue of his subjectivistic conception of the time in which contradictory propositions can be uttered. Marsilius criticises the conception of time held by Buridan. Keywords:Aristotle; John Buridan; Marsilius of Inghen; Metaphysics ; philosophy; principle of non-contradiction