In the study of language, a distinction is made between persuading and convincing. To persuade someone is to induce one to act, whether physically to do something or mentally to believe something. To convince, on the other hand, is to show the reasons something should or should not be acted upon. In the traditional scheme of the first three liberal arts, called the trivium, after grammar comes logic, the art of reasoning, and then rhetoric, the art of persuasion. And that order is important. As C. S. Lewis says in his study The Discarded Image, grammar teaches one how to talk, logic teaches one how to talk sense, and rhetoric teaches one how to talk sense with style. Each study must complement the other two, thereby forming a trivium, a corner in our mind where three roads meet.
Monroe Beardsley was an American philosopher of art, and early in his career he wrote an introductory work on critical reflection entitled Thinking Straight: Principles of Reasoning for Readers and Writers. Originally published in 1950, Monroe’s text is still available and worth the study. He explains “the nature of thinking that is cogent and effective because its steps have a logical order,” and he begins by making clear the often confused difference between the practical logic he is about to teach and rhetoric, its countervailing discipline:
To regard a piece of language from the rhetorical point of view is (in one good sense of this term) to take an interest in its persuasiveness. Will it in fact get the voters to pull the top lever? Will it sell quantities of Chocolate Malted Soy Bubble breakfast cereal? Will it win the debate, or the trial? These are questions for the rhetorician: He is concerned to discover general principles governing the use of words for getting people to believe or feel or act. The logician is not concerned with what actually persuades, but with what ought to persuade; he inquires…not whether in the ‘making of a president,’ a successful ‘image’ is projected to the electorate, but whether a plausible case has been made out for voting one way rather than another…. Rhetoric studies persuasiveness; logic studies convincingness—but remember that the logical question is never ‘Will it actually convince?’ but…’Should it convince?’.
If such a plea for reason and clear-mindedness strikes our skeptical and overadvertised, postmodern minds as hopelessly ideal, then perhaps it is time finally that we reconsider the virtues of idealism. That term, setting aside its strict philosophical definition, refers to the pursuit of an ideal, a standard of excellence which shows the direction in which one should think and will and act, whether that goal is regularly or can ever be realized in the dispensation we inhabit. Without idealism, even under this common definition, we foreclose the possibility of happiness, because that inalienable human aspiration depends upon order, the groundwork of reason and critical understanding.
If instead, though, we decide to pursue our happiness by unreasonable self-assertion alone—I want what I want because I want it and I know what is true because I know it—then only those of us who are sufficiently willful for a time will enjoy happiness, chimeric though it be. For the traditional point of the study of logic is to direct our emotions and their rhetorical imaginings toward what is constant and orderly, peaceable and true.
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