That contrary force must be something other than reason, such as a calm passion like a general appetite for the good, benevolence, or aversion to evil

A second argument, which builds on the first, aims to show that reason “can never oppose passion in the direction of the will” (T 2.3.3.1). The only thing that can oppose an impulse to action generated by one passion is a contrary impulse. Reason, then, could counteract an impulse to action generated by a passion if and only if reason could itself generate a contrary impulse. But from the first argument, we know that that reason cannot generate such an impulse. “Thus it appears, that the princip