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)