Rav Nahman in the LeM vol. I chapter 72 holds that there is a continuum of the evil inclination from the very bottom of physical desires up until the angel of God [the Samech Mem/ aka the Satan]
This subject you can see also in the Letter of Musar of Rav Israel Salanter where he brings down that some Rishonim held the evil inclination to be physical desires. [But no completely physical. After all there are plenty of desires that are connected with our biology that are not physical completely but not spiritual either. E.g., the desire for power or honor. These desires we share with many species of animals like baboons as Sapolsky noticed. I even recall the picture of one beta baboon that dis-respected the alpha baboon. His pieces were found the next morning strewn all over the place.
But there is also the evil inclination that is spiritual--the desire to do what is wrong because it is wrong, The "imp of the perverse" as Edgar Allan Poe calls it.
