This dissertation project concerned philosophical psychology and epistemology, and their metaphysical underpinnings in the late Middle Ages, focussing on critiques of cognitivist arguments for the immaterial nature of the human mind.


The problem of intentionality is an integral part of the discussion about the nature of the human mind or intellect not only in contemporary, but also in mediaeval philosophy. What does possessing an intellect mean? How can the intellect understand other things like material objects in terms of singular and universal cognition? How can it have knowledge of itself? 

In late mediaeval philosophical psychology, it was customary to link intellective cognitive faculties with the immaterial or non-physical nature of the intellect. This primarily involves using arguments from cognition theory to answer the question of the ontological status of the intellect. Alternatively, by taking the immaterial nature of the intellect as its basis, conclusions are drawn about its cognitive achievements. 

However, the validity of these arguments began being questioned over the course of the 13th until the end of the 14th century by various thinkers and, most explicitly, by John Buridan (c. 1300–c. 1358), Master of Arts at the University of Paris. Buridan rejects traditional proofs for the immaterial nature of the human intellect, and gives a materialistic account of its nature within philosophical boundaries. These are nevertheless challenged by theology that considers the intellect, a supernatural product, to be immaterial and everlasting. However, as Buridan makes clear, these theological strictures should not be taken as the foundation of epistemology when explaining different modes of human understanding, such as singular and universal cognition of extra-mental things as well as of the human soul itself.

This dissertation project was successfully completed in 2015 within the program “History of Ancient Science” (HistAS) of the Berlin Graduate School of Ancient Studies (BerGSAS).


Martin Klein, Johannes Buridans Philosophie des Geistes, Leiden: Brill, [inpress]