- Informal logic
**Informal logic**(or, occasionally,**non-formal logic**) is the study of arguments as presented in ordinary language, as contrasted with the presentations of arguments in an artificial, formal, or technical language (see "formal logic"). Informal logic emerged inNorth America in the early 1970s as an alternative approach to the teaching of introductory logic courses to undergraduate students. It quickly became affiliated with theThinking Skills Movement [*Resnick, 1989*] and especially withcritical thinking (see below). Later still it became affiliated with the interdisciplinary inquiry known asArgumentation theory .The precise nature and definition of informal logic are matters of some dispute. 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 in everyday discourse."Johnson, Ralph H., and Blair, J. Anthony (1987), "The Current State of Informal Logic", "Informal Logic", 9(2–3), 147–151.] This definition reflects what had been implicit their practice and what others [*Scriven, 1976*] [*Munson, 1976*] [*Fogelin, 1978*] were doing in their informal logic texts.**Origins and theory**To appreciate this switch in focus from formal to informal logic, one must set aside stock examples such as: "All men are mortal,

Socrates is man, therefore Socrates is mortal." This is not the sort of matter people choose to argue about in their everyday lives; there is nothing to argue about, since the conclusion necessarily follows from the premises. (It is a paradigm of a certain kind of reasoning, called asyllogism ). In the wider world, people argue about which party should form the government, how to deal with global warming, the morality of capital punishment, or the effects of television, subjects that do not lead to answers that have only a single "truth", or "falseness", as do statements within formal logic. In informal logic, argument is distinguished from implication andentailment , argument being construed as activity or discourse in which reasons are given to persuade rationally.The following is an example of such an argument.

Martin is defending the claim that Windsor is not grimy by offering his reasons. But the conclusion has to be extricated from the text; and Martin makes no claim about the strength of his argument, which is typical. His argument makes use of assumptions that need to be unearthed—as is also typical of arguments as they occur in daily life. And there are problems of interpretation, i.e. what he meant by "grimy." This example is typical of the sorts of argument dealt with by informal logic and presents a contrast with the Socrates example.In (2000), Johnson and Blair modified their definition, and broadened the focus now to include the sorts of argument that occurs not just in everyday discourse but also disciplined inquiry—what Weinstein (1990) calls "stylized discourse." The following is Anselm’s

ontological argument —an attempt to persuade the receiver of the truth of theproposition thatGod exists.To understand this 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 to Barth and Krabbe (1982:14f) where they distinguish three senses of the term "form." By "form

^{1}," Barth and Krabbe mean the sense of the term which derives from thePlato nic 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 (orAristotelian ) 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 "form

^{2}," Barth and Krabbe mean the form of sentences and statements as these are understood in modern systems of logic. Herevalidity is the focus: if thepremise s 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 "form

^{3}," 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 formality^{3}of all kinds and under all circumstances." Rather "we defend the thesis that verbaldialectic s 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 argumentativediscourse 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.Some dissent from the view that informal logic is not a branch or subdiscipline of logic. [

*Massey, 1981*] [*Woods, 1980*] [*Woods, 2000*] Massey criticizes the study on the grounds that it has no theory underpinning it. Informal logic, he says, requires detailed classification schemes to organize it, whereas in other disciplines the underlying theory would provides this structure. 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, likepsychology , than to philosophy and logic. [*Massey, 1981*]**Relation to formal logic**Logic is the normative study of

reasoning (q.v.). Wherever there is reasoning, there is a logic that seeks to articulate the norms for that type of reasoning. Informal logic differs from formal logic not only in its methodology but also by its focal point. That is, the social, communicative practice of argumentation can and should be distinguished from implication (or entailment)—a relationship between propositions—which is the proper subject of formaldeductive logic; 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 argument/ation, as distinguished from implication/inference. [*Johnson, 1999*]**Relation to critical thinking**Since the 1980s, informal logic has been partnered, in the minds of many, with critical thinking and indeed some seem to equate the two. Still, it is clear that they are different, though related. Critical thinking is, in the first instance, a kind of activity, or mental practice, whereas informal logic is a kind of inquiry or theory. Critical thinking also designates an educational ideal that 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. The precise definition of "critical thinking" is a subject of much dispute [

*Johnson, 1992*] but there is agreement that in order to think critically one must be able to process arguments. That is where informal logic comes into play. 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. [*Johnson, 1992*] While much of critical thinking will focus on arguments (because one has to grapple with reasons for and reasons against) and hence require skills of argumentation, critical thinking requires additional abilities not supplied by informal logic: the ability to obtain and assess information, to clarify meaning. Also many believe that critical thinking requires certain dispositions. [*Ennis, 1987*] Many succumb to the temptation to conflate critical thinking with problem solving. Johnson takes these issues to be part of the Network Problem [*Johnson, 2000*] and to require, for their proper settlement, a theory of reasoning.**Relation to argumentation theory**"Argument" is not the same as "argumentation" but scholars do not agree on just how these terms should be used. In the approach taken here, argumentation refers to a

social andcultural practice whose chief components are the process of arguing and the product—the argument—which may emerge from that process. But, Pragma-dialecticians, for example, use "argumentation" where many would use "argument". [*van Eemeren and Grootendorst, 1992*] 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 understanding. A full appreciation of argumentation requires insights from logic (both formal and informal), rhetoric, communication theory, linguistics, psychology, and, increasingly, computer science. Since 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, [*Wenzel (1990)*] 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.**See also***

Argument map

*Informal fallacy

*Inference objection

*Lemma**Footnotes****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.

*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**External links*** Groarke, Leo (2002), [

*http://plato.stanford.edu/entries/logic-informal/ Informal Logic*] , "Stanford Encyclopedia of Philosophy "

* [*http://www.napoletano.net/front/node/350 "An informal fallacy primer"*] -- Introduces informal logic and reviews the major fallacies

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**informal logic**— noun that branch of logic whose task is to develop non formal standards, criteria, procedures for the analysis, interpretation, evaluation, criticism and construction of argumentation in everyday discourse … Wiktionary**Logic (disambiguation)**— Logic is the study of the principles and criteria of valid inference and demonstration.Logic may also refer to:In logic and mathematics*A branch of logic: **Inductive logic, also called induction or inductive reasoning **Informal logic, the study … Wikipedia**Logic**— For other uses, see Logic (disambiguation). Philosophy … Wikipedia**Informal mathematics**— Informal mathematics, also called naïve mathematics, has historically been the predominant form of mathematics at most times and in most cultures, and is the subject of modern ethno cultural studies of mathematics. The philosopher Imre Lakatos in … Wikipedia**informal**— mid 15c., lacking form; not in accordance with the rules of formal logic, from IN (Cf. in ) (1) not, opposite of + FORMAL (Cf. formal). Meaning irregular, unofficial is from c.1600. Sense of done without ceremony is from 1828. Related: Informally … Etymology dictionary**logic, philosophy of**— Philosophical study of the nature and scope of logic. Examples of questions raised in the philosophy of logic are: In virtue of what features of reality are the laws of logic true? ; How do we know the truths of logic? ; and Could the laws of… … Universalium**logic, history of**— Introduction the history of the discipline from its origins among the ancient Greeks to the present time. Origins of logic in the West Precursors of ancient logic There was a medieval tradition according to which the Greek philosopher … Universalium**Informal fallacy**— An informal fallacy is an argument whose stated premises fail to support their proposed conclusion. [Kelley, D. (1994) The Art of Reasoning . W W Norton amp; Company, Inc. ISBN 0 393 96466 3] The deviation in an informal fallacy often stems from… … Wikipedia**logic**— noun 1) this case appears to defy all logic Syn: reason, judgment, logical thought, rationality, wisdom, sense, good sense, common sense, sanity; informal horse sense 2) the logic of their argument Syn: reasoning … Thesaurus of popular words**informal fallacy**— noun A fallacy whose error cannot be represented by the symbols used in formal logic. Ant: formal fallacy … Wiktionary