From Chapter Six: "The Poverty of Formalism," pp. 83-84

      For most of this century logic has been regarded as formal logic. And yet philosophers have also assumed that logic provides us with the concepts and norms we need for evaluating arguments. Over the last twenty years the multitude of texts, papers, and courses on informal logic and critical thinking teach an important lesson: we cannot have it both ways. Either logic is identified with formal logic and does not give us the standards we need for assessing arguments in natural language, or logic may give us such standards and is not to be identified with formal logic.

     Arguments are attempts to justify claims, to rationally persuade others or ourselves, on the basis of evidence and reasons, that those claims are true, or acceptable for good reasons. Arguments are put forward in contexts in which the conclusion claim is controversial or can be made to seem doubtful. For the most part, arguments are not stated formally in the symbols of the propositional calculus or any other system of formal logic. They are stated in some natural language—a language rich with metaphor, ambiguity, and vagueness, and adaptable to many different contexts of use. Formal logic is not the right tool for evaluating the arguments of everyday life—or most academic disciplines—for many reasons. Such arguments can be translated into formal terms only with difficulty and with much loss of meaning; many are not deductive in type and thus would not appropriately be appraised with the tools of formal deductive systems even if good translations were possible; premises cannot be evaluated formally; and the social and dialectical context of arguments, within which they need to be understood, is not a formal matter.

    Natural arguments often seem to be better or worse—to have degrees of strength or cogency. Formal logic provides for no such graded evaluations. As evaluated formally, inferential merit is an all-or-nothing matter. Either an argument is valid or it is not. Formal logic makes no provision for taking context into account; nor does it make any provision for relativity to persons—for the possibility that, given different situations, values, and belief systems, an argument might give one person good reason to endorse a conclusion while at the same time not providing good reasons to another.

     If logic is regarded only as formal logic, then logic has at best a modest bearing on the evaluation of natural language arguments. If logic is only formal logic, then logic is useful only for appraising the inference from premises to conclusion in a subset of arguments, those properly regarded as aiming for deductive validity, and translatable, with reasonable accuracy, into formal terms. Rather than restricting logic to formal logic and paying the price of renouncing the claim of logic to be an important tool for the evaluation of arguments, we may endorse a broader conception of logic (one which has good historical credentials, since it is prominent in the work of Aristotle) and maintain the connection between argument appraisal and logic. Such is the orientation of those who work in informal logic.

     The negative adversariality which so often accompanies argument is indeed a matter for concern. It has to be acknowledged that many people, including many philosophers, do argue in an adversarial, closed-minded, and virtually hostile way—and that this style of argument is unlikely to be of value in informing political practice so as to carefully establish common ground and socially reasoned political judgments. Training in critical thinking is immensely valuable in making us sensitive to ambiguities, fallacies, hasty inferences, and problematic premises. But if our responses to others are primarily defensive and negative, serving only to protect our own beliefs from "attack," then their usefulness as tools for building reasonable common ground will be limited.

     We can respond to the adversariality issue in two stages. First of all it is crucial to note that in addition to the adversarial, even militaristic aspects of much argumentative practice, there are other aspects of argumentative practice expressive of respect for persons and other minds. To argue one’s point may seem closed-minded in implying that one is right and has to bring others around. But if we look more closely, we see something else in argument: the bringing forward of evidence and reasons in an effort to rationally persuade another person that the conclusion claim is acceptable. The other person is addressed as a rational being, as a person with beliefs and values of his own, as one who thinks and is capable of changing his beliefs on the basis of reasons and evidence. To present someone with an argument is to attend to his or her mind and thinking processes and to do so in a non-manipulative way. It is to honestly acknowledge differences of opinion and belief, not to skirt over them, hide them, or seek to avoid them by using slogans, loaded terminology, or visual imagery instead of argument. To present others with arguments is to show respect for them as autonomous thoughtful people.

     Contrary to what some feminists have alleged, rational persuasion is not in essence coercive: the other party is always free to reject premises and conclusions. No argument or arguer will force anyone to change her mind. She will change her mind, if at all, because she is convinced or persuaded. Disagreement is openly and honestly acknowledged and respectfully attended to. Thus the attempt to persuade by argument is not manipulative in nature. To present others (and, on occasions, ourselves) with arguments is to invite reflection and provide some of the material for it. When arguments are put forward in a polite, non-hostile way, in reasonable tones and without epithets and insults, back-and-forth, argument need not be confrontational and aggressive. We can argue for a claim without arguing against a person. There are non-adversarial aspects of argument. And there are non-adversarial metaphors for argument—arguments may help us build a case, explore a topic, or think through a problem. Evaluating arguments may lead us to change our own minds; a critical analysis of someone else’s case is not, by definition, a negative one.