Dialectic is the art of logical argumentation. It has been a sister discipline to rhetoric since before Aristotle. Like rhetoric, dialectic is concerned with persuasion and logical proof and takes into account opposing viewpoints on a given issue (see in utrumque partes).

However, unlike rhetoric, dialectic is restricted to issues of argumentation, proof, and the methods and fallacies of logical reasoning. Dialectic does not theorize the use of emotion (except as a fallacy), nor does it concern itself with audiences or with contexts (see kairos) as does rhetoric.

At times in the history of rhetoric dialectic has been conceived of as a counterpart (antistrophos) to rhetoric; at times, it has competed with rhetoric. Those who have emphasized the centrality or priority of dialectic over rhetoric (such as Plato or Peter Ramus in the Renaissance) have done so by reducing rhetoric to being concerned only with style, or with managing appearances and manipulating audiences.

Rhetoric has borrowed from dialectic several terms relating to argumentation, including pistis (proof), apodeixis (logical demonstration), and enthymeme (informal reasoning).