PPT Slide
Ancient & Medieval Philosophy -- David L. Rouse
The power of speech over the constitution of the soul can be compared with the effect of drugs on the bodily state: just as drugs by driving out different humours from the body can put an end either to the disease or to life, so with speech: different words can induce grief, pleasure or fear; or again, by means of a harmful kind of persuasion, words can drug and bewitch the soul.
If Helen was persuaded by love, defense is equally easy. What we see has its own nature, not chosen by us; and the soul is impressed through sight.