The Parasite Tychiades (54)

TYCHIADES But, Simon, at least he is likely to be distressed by lack of food.

SIMON You fail to understand, Tychiades, that a priori: one who lacks food is not a parasite. A brave man is not brave if he lacks bravery, nor is a sensible man sensible if he lacks sense. On any other supposition . the parasite would not exist; and the subject of our investigation is an existent, not a non-existent parasite. If the brave man is brave for no other reason than because he has bravery at his command, and the sensible man because he has sense at his command, so, too, the parasite is a parasite because he has food at his command; consequently, if this be denied him, we shall be studying some other sort of man instead of a parasite.

TYCHIADES Then a parasite will never lack food?

SIMON So it appears; therefore he cannot be distressed, either by that or by anything else whatsoever.