Mind and Soul
The area of philosophy that underwent the most significant development in the early modern period was the philosophy of mind. This was due above all to the work of Descartes. Whereas Cartesian physics had a short and inglorious life, Cartesian psychology was widely adopted and to this day its influence remains powerful in the thinking of many who have never read his work or who explicitly reject his system.
Descartes redrew the boundaries between mind and body, and introduced a new way of characterizing the mental. Since his time it has been natural for philosophers and scientists to structure psychology in a way quite different from that employed by his Aristotelian predecessors in the Middle Ages and the Renaissance.1 This has affected even everyday thinking about human nature and about the natural world.
The Aristotelians regarded mind as the faculty, or set of faculties, that mark off human beings from other animals. Dumb animals share with us certain abilities and activities: dogs, cows, and pigs can all, like us, see and hear and feel; they have in common with us the faculty or faculties of sensation. But only human beings can think abstract thoughts and take rational decisions: they are set off from other animals by the possession of intellect and will. It was these two faculties which, for the Aristotelians, essentially constituted the mind. Intellectual activity was in a particular sense immaterial, whereas sensation was impossible without a material body.
1 See vol. II, Ch. 8.