Is the human intellect material? Or can we show by appeal to its intentional operations, such as universal cognition and self-knowledge, that it is immaterial? Is there therefore a connection between intentionality and immateriality? In Philosophie des Geistes im Spätmittelalter , Martin Klein offers a comprehensive account of John Buridan’s philosophy of mind considered in relation to his epistemology, metaphysics and natural philosophy. In light of material that has only recently been edited, Buridan is presented in the context of the late medieval debate about the nature of the human intellect and how this influences its cognitive functioning.