 Gregory answered with a rigorous and lengthy defense of Bivalence and an alternative modal theory. His defense of Bivalence includes a detailed set of rules for propositions. It is significant that this section of Gregory’s text, some seven pages, stems from Francis of Marchia’s refutation of Auriol’s position, a refutation adopted and extended by Gregory’s own Augustinian predecessor at Paris, Michael of Massa. In short, Gregory argued that the Principle of Bivalence applies universally, and Aristotle was wrong to make an exception in the case of future-contingent propositions. Although this was his basic disagreement with Auriol, Gregory was so careful a philosopher that before he refuted Auriol on this point he corrected his Franciscan predecessor on details and in so doing made Auriol’s own theory more precise.