  In psychology, the study of moving beings qua animate, Buridan changed the Aristotelian paradigm in important ways. In contrast with Thomas Aquinas, who wanted to attribute metaphysically more robust qualities, such as per se subsistence, to the human soul, Buridan does not think that psychology is in a position to reveal anything about the inherent nature of its subject, and so he refuses to speculate about it (Zupko 2007a). He sees the science of psychology as concerned not with some quidditative concept of the soul arrived at by a priori reasoning, but with specifying the relation between animate qualities and the soul as their proper subject: “the natural philosopher only studies substances in relation to their motion and operations (see Zupko 2007b, 2008, 2017ab). And since natural forms require for their operations a determinate matter made suitable for them by qualitative and quantitative dispositions, natural scientists must define forms through their proper matter. Therefore, in its natural definition, the soul must be defined by means of a physical, organic body” (QDA II.3). This led to an even more attenuated conception of the soul in the De anima commentaries of Buridan's Parisian successors, Nicole Oresme and Peter of Ailly, for whom the soul functions as a kind of placeholder whose nature is not even relevant to psychology. Consideration of the soul's ultimate nature migrated to the faculty of theology, where it was considered along with the same Augustinian dreaming arguments that undoubtedly influenced Descartes (See Zupko 1999 and 2003, chs. 10–11).