The paper is devoted to the sophistic method of "two-fold arguments" (antilogic). The traditional understanding of antilogic understood as an expression of agonistic and eristic tendencies of the sophists has been in recent decades, under the influence of G.B. Kerferd, replaced by the understanding of antilogic as an independent argumentative technique, having its own sources, essence, and goals. Following the interpretation of G.B. Kerferd, according to which the foundation of the antilogic is the opposition of two logoi resulting from contradictions (...) or opposites, necessarily associated with the contradictory character of the sensual world, in the paper it is argued that the philosophical basis of antilogic should be sought in the presentation of the views attributed to Protagoras and "adherents of flux" in Plato's dialogue Theaetetus. (shrink)