The common view of language in the West is that it represents the world. Although it is widely recognized that this concept of language originates with Plato, until now, it has not been established how Plato invented this now ubiquitous understanding. Seeming and Being in Plato’s Rhetorical Theory illuminates how, over the course of several dialogues (Gorgias, Phaedrus, Protagoras, Theaetetus, Cratylus, Euthydemus, Republic, and Sophist), Plato creates the concept of language-as-statement in order to overpower the political influence of the sophists. This was the original determination that language could be either false or true, where the distinction between false and true rests on a deeper distinction between seeming and being, or appearance and reality—crucial determinations for Plato’s defeat of the sophists’ false speech. This innovation was made possible through common methods of rhetorical theory; namely, the analysis of written texts and the development of theoretical, meta-discursive vocabulary about discourse, or language about language. Through the linguistic analyses offered in the Republic, the Cratylus, and the Sophist, Plato develops his rhetorical taxonomy of mimêsis, onoma, rhêma, and logos—the terminological foundation for his rhetorical theory of the statement, and of statements being either true or false. In demonstrating how Plato invented what Michel Foucault famously called the “sovereignty of the signifier” this book overturns the common assumption that Plato was rhetoric’s most hostile critic. On the contrary, his rhetorical theory makes it possible for him to establish the sovereignty of the signifier over and against the sovereignty of the sophists.