Neither can the rational faculty or the so-called mind be the motor power, for the speculative intellect never thinks upon what is to be done, or suggests aught concerning what should be fled from or pursued after; but this motion is the act of one fleeing from or pursuing after something. Nor does that faculty, even when reflecting upon any such object, at once bid to flee from or to follow after it, as it often dwells upon something terrible, or agreeable, without suggesting alarm, although the heart may be set in motion or some other part of the impression be agreeable. Add to this, that although the mind may bid, and the reason suggest that something should be fled from or pursued after, the individual does not necessarily move, but acts as does an intemperate person, according to the dictates of passion. It is thus, occasionally, we see that a physician, although versed in medical science, does not cure, as if there were something other than the science which had the power of acting according to the precepts of the science.
It may be affirmed that the appetite cannot be the positive cause of this motion; for the temperate, even while desiring and yearning after something, do not act in order to secure that for which they feel appetite, but follow their understanding.