Abstract

In a 1642 letter to Regius, Descartes elaborates several reasons for rejecting Aristotelian substantial forms including that (1) they are explanatorily impotent, (2) they are explanatorily unnecessary, and (3) they threaten the incorporeality and immortality of the human soul. Various ideas have already been proposed as to why Descartes thought Aristotelian substantial forms are susceptible to these criticisms. Here I suggest one further such idea, centered on the ways Descartes and medieval scholastics thought substantial forms—and souls in particular—are related to their powers.