In his introduction to Avos (Shmomneh P'rakim), the Rambam delineates 5 "parts" of the human nefesh. Is this something that he came to on his own or does he have a source for this?
I know that the Rambam was well versed in both ancient and what was then contemporary philosophy and that it's very likely that this idea came from one of those sources. However, the bit of research I did on this did not turn anything up on this specific point.