As only small portions of the sophists' writings have survived they are mainly known through the works of Plato. Plato's dialogs present his generally hostile views on the sophists' thought, due to which he is largely responsible for the modern view of the sophist as an avaricious instructor who teaches deception.

Before Plato, the word "sophist" could be used as either a respectful or contemptuous title. It was in Plato's dialogue, Sophist, that the first record of an attempt to answer the question "what is a sophist?" is made. Plato described sophists as paid hunters after the young and wealthy, as merchants of knowledge, as athletes in a contest of words, and purgers of souls. From Plato's assessment of sophists it could be concluded that sophists do not offer true knowledge, but only an opinion of things. Plato describes them as shadows of the true, saying, "the art of contradiction making, descended from an insincere kind of conceited mimicry, of the semblance-making breed, derived from image making, distinguished as portion, not divine but human, of production, that presents, a shadow play of words—such are the blood and the lineage which can, with perfect truth, be assigned to the authentic sophist". Plato sought to distinguish sophists from philosophers, arguing that a sophist was a person who made his living through deception, whereas a philosopher was a lover of wisdom who sought the truth. To give the philosophers greater credence, Plato gave the sophists a negative connotation.[22]