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The precise nature and definition of informal logic are matters of some dispute.^[1] Ralph H. Johnson and J. Anthony Blair define informal logic as "a branch of logic whose task is to develop non-formal standards, criteria, procedures for the analysis, interpretation, evaluation, criticism and construction of argumentation."^[2] This definition reflects what had been implicit in their practice and what others^[3][4][5] were doing in their informal logic texts.

Informal logic is associated with (informal) fallacies, critical thinking, the Thinking Skills Movement^[6] and the interdisciplinary inquiry known as Argumentation theory.

Contents 1 Informal logic, formal logic and (informal) fallacies 2 A theoretical background 3 Criticism 4 Relation to critical thinking 5 Relation to argumentation theory 6 See also 7 Footnotes 8 References 9 External links

[edit] Informal logic, formal logic and (informal) fallacies

Logic is the study of inference. In formal logic, the form of an argument either matches or does not match one of the forms of proper inference (or, the conclusion can be derived from the premises using accepted rules of derivation, or by some other formal method.) Informal logic, by contrast, invites us to think about the inference without formalizing it to any (great) extent.

As an example of the difference between formal and informal logic, consider how each would evaluate the argument "The (U. S.) President says it will rain this afternoon at the White House. So, it will rain this afternoon at the White House." In evaluating the inference informally, we think about how the premise ("The President says it will rain this afternoon at the White House.") could be true and yet the conclusion ("It will rain this afternoon at the White House.") could be false. The basic problem with this argument is that we doubt that the President is a reliable indicator of the weather, but we accept what people say only if we think that they are experts on the subject in question and trustworthy. Thus, in addition to the fact that he says it will rain, we would also need to be assured of claims such as "The President is an expert on weather." and "The President is unbiased." and perhaps various others. We are then led to think about the meaning and truth of these additional propositions, in addition to the original premise and conclusion.

To evaluate this argument using formal logic, we would abstract (at least some of) the concrete information from the premises and conclusion and compare the form generated against the forms (or: patterns) of inference which we have predetermined as having a strong connection between premise(s) and conclusion. If we abstract away as much as possible we get (perhaps) "Asserter-A asserts "Proposition-p". So, Proposition-p."^[7] We then check to see if this form is included in our catalogue of accepted inference forms. If it is not, we reject the argument. This particular argument's form would not be found, and so the conclusion would not be accepted (on the basis of this argument, at least.)

Informal logic is often taught as (or at least importantly includes) instruction in a series of "fallacies". These "fallacies" particularly concern modes of argumentation which are not generally covered in formal logic, (though those treated formally can also be treated informally.) These are sometimes expressed in English and sometimes in quasi-formal language, but in all expressions the "fallacies" require further work of the type described in the example above. Govier (1987) writes, "The informal fallacies, historically a central topic for informal logic, involve mistakes in reasoning which are relatively common, but neither formal nor formally characterizable in any useful way."

Although formally these are all fallacies, these so-called "fallacies" are not always fallacious in the context of informal logic. For example, the WP page on informal fallacies defines Argument from Authority as an argument in which "an assertion is deemed true because of the position or authority of the person asserting it." It could also be expressed in quasi-formal language as an argument which moves from the premise "Authority-A asserts "Proposition-p"" to the conclusion "Proposition-p". Even when understood using the quasi-formal expression, however, the intent is that we evaluate the inference in light of the concrete content of the argument. For example, the argument "The President says it will rain. So, it will rain." might be said to be a fallacious appeal to authority. On the other hand, the argument "The President says his dog is sad. So, his dog is sad." might be said to be a correct appeal to authority. The precise content of the argument (in this case, whether it concerns the weather or the mood of his dog) is important, since the President will be understood as an expert about the latter but not the former.

[edit] A theoretical background

To understand the definition above, one must understand "informal" which takes its meaning in contrast to its counterpart "formal." (This point was not made for a very long time, hence the nature of informal logic remained opaque, even to those involved in it, for a period of time.) Here it is helpful to have recourse^[8] to Barth and Krabbe (1982:14f) where they distinguish three senses of the term "form." By "form¹," Barth and Krabbe mean the sense of the term which derives from the Platonic idea of form—the ultimate metaphysical unit. Barth and Krabbe claim that most traditional logic is formal in this sense. That is, syllogistic logic is a logic of terms where the terms could naturally be understood as place-holders for Platonic (or Aristotelian) forms. In this first sense of "form," almost all logic is informal (not-formal). Understanding informal logic this way would be much too broad to be useful.

By "form²," Barth and Krabbe mean the form of sentences and statements as these are understood in modern systems of logic. Here validity is the focus: if the premises are true, the conclusion must then also be true also. Now validity has to do with the logical form of the statement that makes up the argument. In this sense of "formal," most modern and contemporary logic is "formal." That is, such logics canonize the notion of logical form, and the notion of validity plays the central normative role. In this second sense of form, informal logic is not-formal, because it abandons the notion of logical form as the key to understanding the structure of arguments, and likewise retires validity as normative for the purposes of the evaluation of argument. It seems to many that validity is too stringent a requirement, that there are good arguments in which the conclusion is supported by the premises even though it does not follow necessarily from them (as validity requires). An argument in which the conclusion is thought to be "beyond reasonable doubt, given the premises" is sufficient in law to cause a person to be sentenced to death, even though it does not meet the standard of logical validity.

By "form³," Barth and Krabbe mean to refer to "procedures which are somehow regulated or regimented, which take place according to some set of rules." Barth and Krabbe say that "we do not defend formality³ of all kinds and under all circumstances." Rather "we defend the thesis that verbal dialectics must have a certain form (i.e., must proceed according to certain rules) in order that one can speak of the discussion as being won or lost" (19). In this third sense of "form", informal logic can be formal, for there is nothing in the informal logic enterprise that stands opposed to the idea that argumentative discourse should be subject to norms, i.e., subject to rules, criteria, standards or procedures. Informal logic does present standards for the evaluation of argument, procedures for detecting missing premises etc.

[edit] Criticism

Some hold the view that informal logic is not a branch or subdiscipline of logic, or even the view that there cannot be such a thing as informal logic.^[9][10][11] Massey criticizes informal logic on the grounds that it has no theory underpinning it. Informal logic, he says, requires detailed classification schemes to organize it, which in other disciplines is provided by the underlying theory. He maintains that there is no method of establishing the invalidity of an argument aside from the formal method, and that the study of fallacies may be of more interest to other disciplines, like psychology, than to philosophy and logic.^[9]

[edit] Relation to critical thinking

Since the 1980s, informal logic has been partnered and even equated,^[12] in the minds of many, with critical thinking. The precise definition of "critical thinking" is a subject of much dispute.^[13] Critical thinking, according to Johnson, is the evaluation of an intellectual product (an argument, an explanation, a theory) in terms of its strengths and weaknesses.^[13] While critical thinking will include evaluation of arguments and hence require skills of argumentation including informal logic , critical thinking requires additional abilities not supplied by informal logic, such as the ability to obtain and assess information and to clarify meaning. Also, many believe that critical thinking requires certain dispositions.^[14] Understood in this way, "critical thinking" is a broad term for the attitudes and skills that are involved in analyzing and evaluating arguments. The critical thinking movement promotes critical thinking as an educational ideal. The movement emerged with great force in the 80s in North America as part of an ongoing critique of education as regards the thinking skills not being taught.

[edit] Relation to argumentation theory

The social, communicative practice of argumentation can and should be distinguished from implication (or entailment)—a relationship between propositions; and from inference—a mental activity typically thought of as the drawing of a conclusion from premises. Informal logic may thus be said to be a logic of argumentation, as distinguished from implication and inference.^[15]

Argumentation theory (or the theory of argumentation) has come to be the term that designates the theoretical study of argumentation. This study is interdisciplinary in the sense that no one discipline will be able to provide a complete account. A full appreciation of argumentation requires insights from logic (both formal and informal), rhetoric, communication theory, linguistics, psychology, and, increasingly, computer science. Since the 1970s, there has been significant agreement that there are three basic approaches to argumentation theory: the logical, the rhetorical and the dialectical. According to Wenzel,^[16] the logical approach deals with the product, the dialectical with the process, and the rhetorical with the procedure. Thus, informal logic is one contributor to this inquiry, being most especially concerned with the norms of argument.

[edit] See also

• Argument map
• Informal fallacy
• Inference objection
• Lemma

[edit] Footnotes

[edit] References

• Barth, E. M., & Krabbe, E. C. W. (Eds.). (1982). From axiom to dialogue: A philosophical study of logics and argumentation. Berlin: Walter De Gruyter.
• Blair, J. A & Johnson, R.H. (1980). The recent development of informal logic. In J. Anthony Blair and Ralph H. Johnson (Eds.). Informal logic: The first international symposium, (pp.3-28). Inverness, CA: Edgepress.
• Ennis, R.H. (1987). A taxonomy of critical thinking dispositions and abilities. In J.B. Baron and R.J. Sternberg (Eds.), Teaching critical thinking skills: Theory and practice, (pp.9-26). New York: Freeman.
• Eemeren, F. H. van, & Grootendorst, R. (1992). Argumentation, communication and fallacies. Hillsdale, NJ: Lawrence Erlbaum Associates.
• Fogelin, R.J. (1978). Understanding arguments: An introduction to informal logic. New York: Harcourt, Brace, Jovanovich.
• Govier, T. (1987). Problems in argument analysis and evaluation. Dordrecht: Foris.
• Groarke, L. (2006). Informal Logic. Stanford Encyclopedia of Philosophy, from http://plato.stanford.edu/entries/logic-informal/
• Hitchcock, D. The significance of informal logic for philosophy. Informal Logic 20(2), 129-138.
• Johnson, R. H. (1992). The problem of defining critical thinking. In S. P. Norris (Ed.), The generalizability of critical thinking (pp. 38�53). New York: Teachers College Press. (Reprintrf in Johnson (1996).
• Johnson, R. H. (1996). The rise of informal logic. Newport News, VA: Vale Press
• Johnson, R. H. (1999). The relation between formal and informal logic. Argumentation, 13(3) 265-74.
• Johnson, R. H. (2000). Manifest rationality: A pragmatic theory of argument. Mahwah, NJ: Lawrence Erlbaum Associates.
• Johnson, R. H. & Blair, J. A. (1977). Logical self-defense. Toronto: McGraw-Hill Ryerson. US Edition. (2006). New York: Idebate Press.
• Johnson, R. H. & Blair, J. A. (1987). The current state of informal logic. Informal Logic 9, 147-51.
• Johnson, R. H. & Blair, J. A. (1996). Informal logic and critical thinking. In F. van Eemeren, R. Grootendorst, & F. Snoeck Henkemans (Eds.), Fundamentals of argumentation theory (pp. 383-86). Mahwah, NJ: Lawrence Erlbaum Associates
• Johnson, R. H. & Blair, J. A. (2000). Informal logic: An overview. Informal Logic 20(2): 93-99.
• Johnson, R. H. & Blair, J. A. (2002). Informal logic and the reconfiguration of logic. In D. Gabbay, R. H. Johnson, H.-J. Ohlbach and J. Woods (Eds.). Handbook of the logic of argument and inference: The turn towards the practical (pp. 339-396). Elsivier: North Holland.
• Kahane, H. (1971). Logic and contemporary rhetoric:The use of reasoning in everyday life. Belmont: Wadsworth.
• MacFarlane, J. (1995). Logical Constants. Stanford Encyclopedia of Philosophy.
• Massey, G. (1981). The fallacy behind fallacies. Midwest Studies of Philosophy, 6, 489-500.
• Munson, R. (1976). The way of words: an informal logic. Boston: Houghton Mifflin.
• Resnick, L. (1987). Education and learning to think. Washington, DC: National Academy Press..
• Scriven, M. (1976). Reasoning. New York. McGraw Hill.
• Walton, D. N. (1990). What is reasoning? What is an argument? The Journal of Philosophy, 87, 399-419.
• Weinstein, M. (1990) Towards a research agenda for informal logic and critical thinking. Informal Logic, 12, 121-143.
• Wenzel, J. 1990 Three perspectives on argumentation. In R Trapp and J Scheutz, (Eds.), Perspectives on argumentation: Essays in honour of Wayne Brockreide, 9-26 Waveland Press: Propsect Heights, IL
• Woods, J. (1980). What is informal logic? In J.A. Blair & R. H. Johnson (Eds.), Informal Logic: The First International Symposium (pp. 57-68). Point Reyes, CA: Edgepress.
• Woods, J. (2000). How Philosophical is Informal Logic? Informal Logic 20(2): 139-167. 2000

[edit] External links

• Groarke, Leo (2002), Informal Logic, Stanford Encyclopedia of Philosophy
• MacFarlane, J. (2005) Logical Constants, Stanford Encyclopedia of Philosophy
• An informal fallacy primer -- Introduces informal logic and reviews the major fallacies
• BadArguments.org

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