DIALECTICS, in the literary history of the ancients, that branch of logics, which taught the rules and modes of reasoning. See LOGIC, Part III.
Zeno Eleates was the first who discovered the natural series of principles and conclusions observed in reasoning, and formed an art thereof in form of a dialogue; which, for this reason, was called dialectica.
The dialectics of the ancients is usually divided into several kinds; the first was the eleatica, that of Zeno Eleates, which was threefold; viz. consecutionum, colloquutionum, and contentionum. The first consisting of rules for deducing or drawing conclusions. The second, the art of dialogue; which became of such universal use in philosophy, that all reasoning was called interrogation: then, syllogism being laid aside, the philosophers did all by dialogue; it lying on the respondent to conclude and argue from the several concessions made. The last part of Zeno's dialectics, Epicurea, was contentious, or the art of disputing and contradicting; though some, particularly Laertius, ascribe this part to Protagoras, a disciple of Zeno.
The second is the dialectica megarica, whose author is Euclid, not the mathematician, but another of Megara. He gave much into the method of Zeno and Protagoras: though there are two things appropriated to him: the first, that he impugned the demonstrations of others, not by assumptions, but conclusions; continually making illations, and proceeding from consequence to consequence: the second, that he set aside all arguments drawn from comparisons of similitude as invalid.
He was succeeded by Eubulides, from whom the sophistic way of reasoning is said to be derived. In his time the art is described as manifold: mentions, fallens, electra, obvelata, arcevalis, cornuta and calva. See SOPHISM.
The third is the dialectics of Plato, which he proposes as a kind of analysis to direct the human mind by