Prodicus came from the island of Ceos; he was probably born around 470 and died some time after 400. There is an amusing picture of him in Plato's Protagoras (315c–d), lying on a couch. Socrates often refers to Prodicus as his teacher, and some have speculated that Socrates' concern with the precise meanings of words like “justice” may owe something to Prodicus' work on distinctions. In addition to fr. 1, there are also references to Prodicus' fondness for distinguishing between near synonyms in Protagoras 339e–341d, Meno 75e, Euthydemus 277e, and Aristotle, Topics 2.6, 122b22.

(Plato, Protagoras 337a–c; DK A13)

During an interlude in the discussion between Socrates and Protagoras, Prodicus contributes the following.

Those who are present at these discussions should be an impartial but not an egalitarian audience; for these are not the same. You must hear both sides impartially but not give them equal weight; rather, give more weight to the wiser and less to the more foolish speaker. For my own part, moreover, I think you two, Protagoras and Socrates, should agree to debate but not to quarrel; for friends debate with friends in a cordial spirit, but enemies and adversaries quarrel with one another. In this way we will have the best discussion, for you speakers will be esteemed, and not praised: esteem is truly in the minds of the listeners without deceit, whereas praise is often falsely given in words that run counter to one's actual opinion.