Plato—through a fictionalized conversation between Socrates and Sophists such as Gorgias—defines rhetoric in the context of sophistry. Rhetoric is concerned with persuasion through speech. In the dialogue, Gorgias says to Socrates: rhetoric is “the ability to persuade with speeches either judges in the law courts or statesmen in the council-chamber or the commons in the Assembly or an audience at any other meeting that may be held in public affairs” (91). In other words: rhetoric is a kind of discursive tool of persuasion that, when employed, is for public settings. Socrates clarifies that things other than speech can be persuasive: in this way, rhetoric is concerned only in those instances where speech is used to persuade.
From here, Socrates distinguishes between belief and knowledge (in this case, knowledge being synonymous with true and moral knowledge). In this sophist sense, “rhetoric, it seems, is a producer of persuasion for belief, not for instruction in the matter of right or wrong” (93). Thus, truth—or leading to truth—is effectively taken out of the purpose of rhetorical persuasion. Gorgias offers the example of two speakers: a doctor and a rhetorician, both vying for the job as physician; however, “you would find the physician to be nowhere, while the master of speech would be appointed if he wished” (93). In this case, Gorgias places rhetoric in the public and probable realm. Socrates writes succinctly, “there is no need to know the truth of the actual matters, but one merely needs to have discovered some devices of persuasion which will make one appear to those who do not know or know better than those who know” (95). In this way, Gorgias labels rhetoric a neutral art: capable of doing both the just and the unjust; however Socrates labels it a base art, aligning rhetoric as a “habitude” concerned with “producing a kind of gratification and pleasure” (97).
When the conversation moves to Callicles, both Callicles and Socrates agree that one can employ rhetoric “to get what he wants, but to do so he must flatter convention. He must seek to become similar to his audience in order to persuade them” (83). Thus, a tension exists between truth-seeking and adhering to conventional belief: Plato (via Socrates) understands his duty is to be independent of conventional belief in order to lead others to truth; however, the sophists must adhere to such conventional, public belief in order to persuade. Socrates writes, “Then it is this that our orator, the man of art and virtue, will have in view, when he applies to our souls the words that he speaks, and also in all his actions, and in giving any gift he will give it, and in taking anything away he will take it, with this thought always before his mind—how justice may be engendered in the souls of his fellow-citizens, and how injustice may be removed; how temperance may be bred in them and licentiousness cut off; and how virtue as a whole may be produced and vice expelled. Do you agree to this or not?” (124)