 In offering his spirited and protracted defense of substantial forms, and of formal causation more generally, Suárez shows himself aware of the need to articulate and defend core features of his broadly Aristotelian framework, including some which later came in for harsh criticism. Indeed, in the case of substantial forms, these criticisms were finding voice already during his lifetime; he was, for instance, an older contemporary of Descartes (b. 1596), who was twenty years old when Suárez died in 1617. Descartes simply reports without argument that substantial forms are “a philosophical being unknown to me” (Letter to Morin, 12 September 1638; Descartes 1984: 122). Because he is alert to such concerns, and addresses them directly, Suárez appears to many historians of philosophy as a sort of bridge figure between scholastic and early modern philosophy. That may or may not be so, depending on the principles of periodization presupposed by those offering this sort of judgment. What is clearly true, however, is that he very often develops Aristotelian theses in a manner betraying a willingness to abandon those features of Aristotelianism which were to come in for the harshest treatment by philosophers subsequent to him.