Medieval scholastics share a commitment to a substance-accident ontology and to an analysis of efficient causation in which agents act in virtue of their powers. Given these commitments, it seems ready-made which entities are the agents or powers: substances are agents and their accidents powers. William of Ockham, however, offers a rather different analysis concerning material substances and their essential powers, which this article explores. The article first examines Ockham’s account of propria and his reasons for claiming that a material (...) substance is essentially powerful sine accidentibus. However, the article subsequently argues that, given Ockham’s reductionism about material substance, only substantial forms – never substances – are truly agents and powers. Thus, a material substance is essentially powerful but only by courtesy – per accidens, as Ockham calls it – because it has a non-identical part, its substantial form, which does all the causal work by itself, per se. (shrink)

This paper studies the theories defended by John Buridan and Nicole Oresme on the presence of the soul in the body, with a special focus on the interpretation of the Augustinian principle – or ‘holenmeric’ principle – according to which the soul is in the whole body and is wholly present in every part of it. The first part of the paper introduces the different types of composition involved in the medieval discussions over the soul and its parts and shows (...) how different psychological theories prior to 1350 employed this typology of part/whole relations to clarify the soul’s presence in the body. The next part of the paper presents how the theories designed by John Buridan and Nicole Oresme were motivated by problems raised by these earlier accounts of the soul’s presence and undertook to solve them from the perspective of a reductionist conception of parthood. It is argued that, despite their common commitment to a reductionist stance, the solutions endorsed by Buridan and Oresme represent two opposite ways of applying a nominalist metaphysics of parts to psychological matters. (shrink)