If, therefore, motion is stated as the genus of pleasure, you should look and see if pleasure is neither locomotion nor alteration, nor any of the rest of the given modes of motion; for clearly it will not partake of any of the species, and therefore not of the genus either, since what partakes of the genus must necessarily partake of one of the species as well; so that pleasure could not be a species of motion, nor yet be one of the individual phenomena falling under a species of motion.