In this dissertation, I survey 13th-14th century debates in medieval psychology and metaphysics, chiefly concerning the activity of the soul and the general nature of causation and causal co-operation. I give particular attention to a few notable “Augustinian” Franciscans, viz., Peter John Olivi, Gonsalvus of Spain, and John Duns Scotus. According to these figures, even our most basic acts of cognition primarily originate from within our cognitive powers, rather than from external objects. This view is motivated by both metaphysical and (...) empirical considerations, such as Neo-Platonic and Aristotelian causal principles and the apparent experiential effects of attention on cognition. As I discuss, active accounts of cognition are also forced to say something about how external objects can nonetheless play some role in cognition, and, thus, end up tied to generally interesting theories of asymmetric causal co-operation. In this survey, I also examine the peculiar Dominican, Durand of St. Pourçain. I argue that despite employing many common arguments and authoritative passages as Olivi, Gonsalvus, and Scotus, Durand offers a more minimal picture of cognition, in some ways, more extreme, but in other ways, more passive. (shrink)