Zabarella's "On Intelligible Species" concerns the role of intentional objects and the various ways in which they have been conceived within the Aristotelian tradition up to the time of the renaissance. In this treatise, Zabarella reviews various positions that have been taken on the role of intentional objects in intellection by the early greek, arabic, medieval and renaissance era commentators. He divides the various positions dialectically into two main groups and proceeds to pose his own view at the end. Thus, the treatise is valuable not only for the Zabarella's personal views, but also for his encyclopedic treatment of the views of earlier commentators including Averroes, Aquinas, Scotus, and Jean of Jandun.