Logic and rhetoric are such broad subjects that in order to profit from their comparison we must make at least one division in each field. Logic in the narrow sense is mainly concerned with the consequence relation (“following from”), and a well-documented tradition exists from Aristotle’s Prior analytics to the present that explores this question. In a wider sense, logic includes the study and statement of the principles of good reasoning and may be seen as taking as its central problem the question of what makes for a good argument or a good inference. Developments of logic in the wide sense can be found as long ago as Aristotle’s Topics and more recently in twentieth-century informal logic.
In the narrow sense, rhetoric deals with the study of persuasive discourse, especially argumentation. Aristotle’s Rhetoric and Perelman’s new rhetoric are prime examples of this. In a wider sense, rhetoric is the art of making things matter (Farrell’s 1998 phrase), especially (but not only) through the effects of language, and includes poetry, drama, narratives, instructional discourse, and the like. It is only when we consider logic in the wide sense and rhetoric in the narrow that their domains can overlap, and that it may become difficult to tell logical and rhetorical considerations apart.
Plato And Aristotle
In Plato we cannot identify any logic apart from what he calls dialectic, but many of the principles that can be extracted from what he says about dialectic also belong to logic in the wide sense. In the Gorgias Plato distinguishes dialectic and rhetoric on two related counts: (1) rhetoric is concerned with appearances and persuasion whereas dialectic is concerned with truth and justice; (2) dialectic is an art (or technê), meaning that it is a teachable and productive activity, and rhetoric is not. At the outset of his later dialogue, Phaedrus, Plato again dismissed certain kinds of rhetoric on moral grounds. But he went on to outline a philosophical kind of rhetoric, which was a way of directing the soul toward knowledge by means of speech. Dialectic was still his preferred method, having the power of leading one to knowledge through its methods of division and collection; however, Plato allows that rhetoric could be based on dialectic when teaching another. It would then be an art because it would presuppose the speaker’s acquaintance with the forms of knowledge and would additionally involve knowledge of the different kinds of souls and the kinds of speeches likely to affect them. The kind of rhetoric of which Plato approves, then, has only a narrow pedagogical range.
In Aristotle, in addition to logic in the wide sense that we see in the Topics, there is also logic in the narrow sense (in Prior analytics), rhetoric in the narrow sense (in Rhetoric), and rhetoric in the wide sense (in Poetics). In all four fields but the last, the concept of syllogism is central to the elaboration of the subjects. Near the beginnings of both analytics and Topics Aristotle defines a syllogism as an argument in which the conclusion (1) follows necessarily from the premises, (2) is different from any of the premises, and (3) comes about because of the premises. (Notice that the extension of “syllogism” is thus much narrower than that of “valid argument.”) In the Prior analytics syllogisms take first principles or their consequences for premises; dialectical employments of the syllogism, however, are identified as those that either are based on answers given to questions in discussions or are widely shared beliefs (endoxa). This last feature is shared with rhetorical uses of the syllogism (these Aristotle calls enthymemes) which are further distinguished by the fact that they do not require that conclusions should follow necessarily from their premises; that they follow for the most part suffices.
Aristotle identified three kinds of rhetoric, distinguishable by the nature of audiences: forensic rhetoric is addressed to courts and concerns events in the past; deliberative rhetoric is addressed to individuals or councils planning for the future; and ceremonial (epideictic) rhetoric is concerned with an audience’s present attitudes or feelings about a person or event.
For Aristotle, rhetoric is the study of the various modes of persuasion and it is an art; he sees it as an outgrowth of both politics and dialectics. However, although he clearly gives an essential role to the enthymeme as being “the substance of rhetorical persuasion,” it seems to play a significant role in only one of the three invented (or internal) modes of persuasion he identified, namely, logos. The other modes were pathos (the use of emotions) and êthos (display of character). His conception of rhetoric in the narrow sense thus appears to be wider than that of logic in the wide sense since he recognizes that rhetoric as an instrument of persuasion will require knowledge of character, ethics, and the emotions, over and above knowledge of logical proofs.
Whately And Perelman
Richard Whately in his Elements of rhetoric (1828) thought of rhetoric as the art of composing arguments. Logic, on the other hand, he took to be both a science that investigated the processes of the mind in reasoning and an art that furnished rules of reasoning to avoid erroneous deductions (see Elements of logic ). He further distinguished inferring and proving. The former belongs to the search for truth and depends on logic, the latter is within the province of rhetoric and is concerned with establishing the truth to the satisfaction of another.
In the twentieth century Chaim Perelman worked to develop a rhetoric that would serve for philosophy as well as public discourse. This was largely in response to the dominance of the logical positivists who extended the innovations in logic in the narrow sense (originally wrought by Frege, Russell, and Wittgenstein to deal with uncertainties in the foundations of mathematics), to serve in the analysis of scientific discourse. But their methods being both formal and positivist were ill equipped to deal with either natural language arguments in public discourse or questions of value – issues that became of increasing concern after World War II. Perelman’s response was to advocate a revival of the subject of argumentation and although it was inspired by both Aristotle’s dialectical and rhetorical views, he referred to his approach as a new rhetoric. It is characterized by the marginalization of logic in the narrow sense as having no relevance to argumentation, and the broadening of the scope of rhetoric to include all natural language argumentation, not just the types that might be addressed to the three kinds of audiences posited by Aristotle.
Perelman saw logic as logic in the narrow sense: it was formal, demonstrative, concerned with truth and validity, and impersonal in its methods. Rhetoric, which he equated with argumentation, however, was concerned with reasonable and justifiable opinions rather than truth, and in contrast to logic, argumentation interacts with the minds of its audience, aiming to persuade or convince it. Arguments, rather than being valid or invalid as logic would have it, argumentation judges as more or less strong.
Perelman’s rhetoric is a rhetoric in the narrow sense but it broadens Aristotle’s approach by extending the object of discourse to any audience addressed (including oneself), and widening the subject of discourse to include the theoretical as well as the practical. He distinguished actual and particular audiences from the abstract universal audience. Actual audiences may be persuaded, but universal audiences – impartial and critical sounding boards constructed by the speaker – hold to a higher standard and will be convinced only by good argumentation.
In response to Perelman, Henry Johnstone, Jr. sought to distinguish philosophical method from rhetorical method. Since the purpose of rhetoric, even as refurbished by Perelman, was to gain assent to a thesis, Johnstone took the rhetor as having the overriding goal of getting his view accepted by his listener. But, Johnstone insists, if the listener is aware that rhetorical techniques are being employed against him, he will be resistant to persuasion. Thus rhetoric can succeed only when it conceals its methods. In contrast, philosophical argumentation must allow any technique used by an arguer to be equally available to her discussant.
Rhetorical And Logical Values
Typically rhetoric exhibits its value in the analysis of speeches like Socrates’ defence in Plato’s Apology or Lincoln’s “Gettysburg address,” uncovering motivations and strategies and persuasive techniques. In contrast, logic paradigmatically seeks to display its excellence in the analysis of arguments such as Anselm’s ontological argument or Hume’s argument against miracles, identifying inferential structures, for example, and modal operators, and searching for ambiguities and missing or unsupported premises.
The central problem of logic in the wide sense is that of when one ought to accept a conclusion given certain reasons. The central problem of rhetoric in the narrow sense is how a set of ideas ought to be presented to an audience, how a presentation can come as close as possible to having its desired effect. Thus logic relies on semantic and epistemic considerations like truth and acceptability whereas rhetoric leans on social and psychological factors such as emotions, tradition and popularity. Accordingly, logic and rhetoric bring distinct sets of standards to argumentative discourse.
But whereas logic champions truth and consistency and puts persuasion at risk, and rhetoric prizes successful communication above logical excellence, neither the logician nor the rhetorician can escape logical or ethical responsibility for their discourses. Broadly speaking there are two kinds of responses to this situation. One is for each subject to incorporate items from the other’s subject when they attempt a comprehensive theory for argument evaluation. Thus many elementary logic books include rhetorical maxims, and many rhetoric primers include a chapter on the elements of logic. Ralph Johnson, the informal logician, extends Johnstone’s requirement for philosophical argumentation to rational persuasion in general: in addition to holding the three standards advocated by many other informal logicians (that the premisses should be acceptable, relevant and sufficient), Johnson stresses that argumentation must not be unilateral but that the argument presented to its addressee should be completely open, with all its features made plain and manifest. The reason for this is that the addressee’s assent to the argument could be rational only if he or she has complete access to the same information and reasoning as the persuader. This awareness of and concern for the persuadee has not in the past been thought to belong to logic, even logic in the wide sense. It is therefore interesting that Johnson’s concern for the epistemic welfare of his interlocutor is raised to the level of a right: the arguer has obligations to those whom he is trying to persuade. This is an example of logic treading on rhetoric’s territory. The other response to the observation that we have both logical and rhetorical responsibilities is suggested by Joseph Wenzel. It is that logic, rhetoric and dialectic are in fact three distinct perspectives on argumentation, each having different scopes, resources and standards, and answering to different interests. Rhetoric, Wenzel maintains, deals with arguments as a process whereas logic treats them as a product. He considers rhetoric a resource to help communities find solutions to practical problems; but with the informal logicians, he sees good arguments as those that give acceptable, sufficient and relevant reasons for their conclusions. Tindale has gone a step further, agreeing with Wenzel that all three perspectives are necessary for a complete analysis of argumentative discourse, but adding also that rhetoric is the basic or most fundamental of the three components.
- Farrell, T. B. (1998). Sizing things up: Colloquial reflection as practical wisdom. Argumentation, 12, 1–14.
- Johnson, R. H. (2000). Manifest rationality. Mahwah, NJ: Lawrence Erlbaum.
- Johnstone, H. W., Jr. (1965). Persuasion and validity in philosophy. In M. A. Natanson & H. W. Johnstone, Jr. (eds.), Philosophy, rhetoric and argumentation. University Park: Pennsylvania State University Press, pp. 138–148.
- Perelman, C., & Olbrechts-Tyteca, L. (1969). The new rhetoric. Notre Dame, IN: University of Notre Dame Press.
- Tindale, C. W. (1999). Acts of arguing. Albany, NY: SUNY Press.
- Wenzel, J. (1990). Three perspectives on argument: Rhetoric, dialectic, logic. In R. Trapp & J. Schuetz (eds.), Perspectives on argumentation. Prospect Heights, IL: Waveland, pp. 9–26.