Dialectical Reasoning in Aristotle’s Theory of Rhetoric

This page sketches the basic features of Aristotle’s conception of dialectical reasoning for the purpose of understanding its role in his theory of rhetoric. (In order to display the ancient Greek correctly, this page contains Unicode character codes. So, if the Greek doesn't look as expected, your computer may need a Unicode polytonic Greek font. Russell Cottrell’s “Unicode Polytonic Greek Fonts” provides links to several free fonts — I recommend Cottrell's own "Aristarcoj.")

Even though Aristotle explicitly defines rhetoric as “the faculty of observing in any given case the available means of persuasion” (1355b), we find in the opening sentence of the Rhetorica that he also understands “rhetoric” in relation to dialectic:

Ἡ ῥητορική ἐστιν ἀντιστροφος τῆ διαλεκτικῆ· ἀμφότεραι γὰρ pερὶ τοιούτων τιῶν εἰσἰν ᾶ κοινὰ τρόpον τινὰ ἁpάντων ἐστἰ γνωρίξειν καὶ οὺδεμιᾶς ἐpιστήμης ἀφωρισμένως. (1354a)

Rhetoric is an antistrophos to dialectic; for both are concerned with such things as are, to a certain extent, within the knowledge of all people and belong to no separately defined science [epistêmês]. (Kennedy 28-29)

A better understanding of Aristotle’s conception of rhetoric, then, would be served by some understanding of this relationship; and, of course, this requires some knowledge of his use of the term dialectic. In order to get a general sense of what Aristotle means by “dialectic,” we first look at his theory of rationality in his Nichomachean Ethics and in his Topics, which takes as its subject matter “dialectical reasoning.” We will find, however, additional problems because of the ambiguity of the word he chose to characterize rhetoric’s relationship with dialectic: antistrophos.

I. Rationality as a Basic Component of Psychê

II. Dialectic as One of Four Types of Reasoning

III. The Syllogism as the Basic Form of Reasoning

IV. Aristotle’s Concept of the Enthymeme

V. Works Cited & Bibliography


I. Rationality as a Basic Component of Psychê

In Book VI of his Nicomachean Ethics, Aristotle outlines a theory of the psychê (soul, spirit) in which rationality is one of two basic categories of behavior:

πρότερον μὲν οὖν ἐλέχθη δὔ εἶναι μέρη τῆς ψυχῆς, τό τε λόγον ἔχον καὶ τὸ ἄλογον· (1139a1)

We said before that there are two parts of the soul -- that which possesses reason [logon] and that which is irrational [alogon]. (Ross 1798)

Aristotle continues by distinguishing two types of rationality, "one by which we contemplate the kind of things whose principles cannot be otherwise, and one by which we contemplate variable things":

λεγέσθω δὲ τούτων τὸ μὲν ἐπιστημονικὸν τὸ δὲ λογιστικόν· τὸ  γὰρ βουλεύεσθαι καὶ λογίζεσθαι ταὐτόν, οὐθεὶς δὲ βουλεύεται περὶ τîν μὴ ἐνδεξομένων ¥λλως œχειν, éste τὸ λογιστικόν ἐστιν ›ν τι μέρος τοà λόγον œχοντος. (1139a6)

Let one of these parts be called the scientific [epistêmonikon] and the other the calculative [logistikon]; for to deliberate [bouleuesthai] and to calculate [logizesthai] are the same thing, but no one deliberates about what cannot be otherwise. (Ross 1798)

Aristotle's Model of the Psyche

II. Dialectic as One of Four Types of Reasoning

Aristotle defines “dialectical reasoning” by comparing it to three other kinds of reasoning. The four kinds are

Aristotle's 4 kinds of reasoning

III. The Syllogism as the Basic Form of Reasoning

For Aristotle, “reasoning” consists in a three-part form in which a conclusion is deduced from two premises, a form known as the syllogism. We can see also that what distinguishes the four types of reasoning from one another is the type of premises used. Here is the traditional example of syllogistic reasoning. Given the type of premises it uses, under which of Aristotle’s four categories does it fall?

All humans are mortal;
Socrates is a human;
therefore, Socrates is mortal.

IV. Aristotle’s Concept of the Enthymeme

When Aristotle characterizes rhetoric as “counterpart of Dialectic,” he means that rhetorical persuasion will be grounded in the kind of premises that define dialectical reasoning. But, if they share the same kind of premises, how is rhetoric different from dialectic? Unfortunately, the discussion of this difference in the Rhetoric is not well developed. But there are a few passages that identify key differences. The first difference is that the rhetorical syllogism, or “enthymeme,” is a truncated syllogism:

The Enthymeme must consist of few propositions, fewer often than those which make up the normal syllogism. For if any of these propositions is a familiar fact, there is no need even to mention it; the hearer adds it himself. (1357a)

It has already been pointed out that the Enthymeme is a syllogism, and in what sense it is so. We have also noted the differences between it and the syllogism of dialectic. Thus we must not carry its reasoning too far back, or the length of our argument will cause obscurity: nor must we put in all the steps that lead to our conclusion, or we shall waste words in saying what is manifest. It is this simplicity that makes the uneducated more effective than the educated when addressing popular audiences-makes them, as the poets tell us, “charm the crownd’s ears more finely.” Educated men lay down broad general principles; uneducated men argue from common knowledge and draw obvious conclusions. (1395b)

V. Works Cited & Bibliography

Works Cited

Selected Bibliography

Carol Poster has compiled an extensive bibliography of mostly twentieth-century scholarship on the enthymeme, “The Enthymeme: An Interdisciplinary Bibliography of Critical Studies,” which is available online at the site of the Journal for the Study of Rhetorical Criticism of the New Testament. The following selected bibliography lists a few articles that I have found time to read and that I believe others will find useful.

A. On Dialectic and Rhetoric

B. On the Enthymeme

Thanks to Alex (a.k.a. “classicalwriter”) and Trish Roberts-Miller for suggestions and observations regarding this page. And thanks to Russell Cottrell; without his Unicode Font Utility, the imputing of Unicode Greek would have been excruciating.

Last update: 8-Aug-04

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Some pages on this site contain material from my classes taught in The Department of English at Middle Tennessee State University.

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