The study of logic has often fostered the idea that its methods mightbe used in attempts to understand and improve thinking, reasoning, andargument as they occur in real life contexts: in public discussion anddebate; in education and intellectual exchange; in interpersonalrelations; and in law, medicine and other professions.

Informal logic is an attempt to build a logic suited to this purpose.It combines accounts of argument, evidence, proof and justificationwith an instrumental outlook which emphasizes their usefulness in theanalysis of real life arguing. Blair 2015 identifies two key tasks forthe informal logician: (i) the attempt to develop ways to identify(and “extract”) arguments from the exchanges in which theyoccur; and (ii) the attempt to develop methods and guidelines that canbe used to assess their strength and cogency.

Though contributions to informal logic include studies of specifickinds or aspects of reasoning, the overriding goal is a generalaccount of argument which can be the basis of systems of informallogic that provide ways to evaluate arguments. Such systems may beapplied to arguments as they occur in contexts of reflection, inquiry,social and political debate, the news media, blogs and editorials, theinternet, advertising, corporate and institutional communication,social media, and interpersonal exchange.

In the pursuit of its goals, informal logic addresses topics whichinclude, to take only a few examples, the nature and definition ofargument, criteria for argument evaluation, argumentation schemes,fallacies, notions of validity, the rhetorical and dialectical aspectsof arguing, argument diagramming (“mapping”), cognitivebiases, the history of argument analysis, artificial intelligence(AI), and the varying norms and rules that govern argumentativepractices in different kinds of contexts.

• 1. History
• 2. Systems of Informal Logic
• 3. Standardizing Arguments
• 4. Testing Arguments
• 5. Informal Logic Within A Broader Context
• 6. Informal Logic and Philosophy
• Bibliography
• Academic Tools
• Other Internet Resources
• Related Entries

1. History

Puppo 2019 provides a recent collection of articles on the history of informallogic and the issues it addresses. In many ways, informal logic as weknow it is a contemporary version of historical attempts to explain,systematize, assess and teach arguing for practical purposes.

In ancient times, the First Sophistic is a movement motivated by thenotion that one can teach the art oflogos in a way that canbe effectively employed in public argument and debate. In the centurythat follows, Aristotle’s logical and rhetorical works —notably thePrior Analytics and theRhetoric —provide a systematic account of logic and argument which is applicableto an impressively broad range of real life arguments. Today, theyremain important works that inform discussions of informal logic.

In modern times,The Port Royal Logic (Arnauld and Nicole1662, originally titledLogic or the Art of Thinking) is anattempt to outline a logic that can guide everyday reasoning. It is acelebrated (and often disdained) introduction to the art of arguingwhich has been published in more than fifty French editions and fivepopular English translations. It understands “logic” as“the art of directing reason aright, in obtaining the knowledgeof things, for the instruction both of ourselves and others”(25). In keeping with this, it provides a practical account of goodand poor argument, discussing fallacies, syllogisms, definitions, anddeductive and probable reasoning, emphasizing real rather thanconcocted examples of argument (see Finocchiaro 1997).

One finds other analogues of contemporary attempts to study and teachinformal reasoning in nineteenth century textbooks on logic andrhetoric. Richard Whately is of special note in this regard. He beganhis career as a professor of political economy at Oxford, wasappointed Archbishop of Dublin, and attempted to establish a nationalnon-sectarian system of education, writing texts on reasoning thatcould promote this cause. In many ways, Whately’sElements of Logic andElements of Rhetoric (1826, 1830) are close analogues ofearly versions of today’s informal logic textbooks.

Another important text, critical of Whately, but in the same broadtradition is Mill’sA System of Logic (1882) (seeGodden 2014). It defines logic as the “art and science ofreasoning,” stipulating that “to reason is simply to inferany assertion from assertions already admitted.” The end resultis a broad account of inference which is, like systems of informallogic, designed to inform real life instances of argument.

The first use of the term “informal logic” occurs in thelast chapter of Gilbert Ryle’s bookDilemmas (1954). Heintroduces it in an attempt to distinguish between formal logic andthe more varied, less strict, and less defined ways in which we needto assess many of the arguments that are used in philosophicaldiscussion.

In North America, the rise of informal logic as it is now understoodis tied to educational trends rooted in the 1960s — a time ofsocial upheaval and protest (most notably, against the War in Vietnam)which produced calls for an education relevant to the issues of theday. This fueled an interest in the logic of everyday argument and theteaching of introductory logic, which was at the time taught withtextbooks like Copi’s popularIntroduction to Logic(1953).

InLogic and Contemporary Rhetoric: The Use of Reason in EverydayLife (1971), Kahane more fully embraced instances of real lifearguing, discussing a wide range of examples in newspapers, the massmedia, advertisements, books, and political campaigns. Other attemptsto provide a general introduction to logic — by Carney andScheer (1964), Munson (1976), and Fogelin (1978) — employed theterm “informal logic” to distinguish between formal logicand other methods of argument analysis which lay outside of it.

The idea that informal logic should be developed as a distinct fieldof inquiry was championed by Johnson and Blair at the University ofWindsor. They published a popular textbook,LogicalSelf-Defense (1977); organized and hosted “The FirstInternational Symposium on Informal Logic” and edited theproceedings (Blair and Johnson, 1980); established theInformalLogic Newsletter (1978-1983); and ultimately turned thenewsletter into the journalInformal Logic (subtitled“Reasoning and Argumentation in Theory and Practice”). Inthis and other ways, they established informal logic as a field forstudy, research and development. Their contributions (and those ofcolleagues at Windsor and in Ontario and Canada) is reflected in thenotion that informal logic is a Canadian (or, more narrowly, Windsor)school of argument (see Puppo 2019).

Much of the discussion that has shaped the evolution of informal logicas a field has taken place in a number of journals that have played amajor role in its development. They includeInformal Logic,Argumentation,Philosophy and Rhetoric,Argumentation and Advocacy (formerly theJournal of theAmerican Forensic Association),Teaching Philosophy, and(more recently)Cogency andArgument andComputation.

A key catalyst that promoted the development of informal logic was the“Critical Thinking” Movement within education (welldescribed in Siegel 1988, Ennis 2011, and Blair 2021). The movementpushed (and continues to push) for educational developments which makethe critical scrutiny of our beliefs and assumptions a fundamentalgoal, highlighting the significance of reasoning, inference, argumentand critical assessment.

In 1980, a California State University Executive Order promoted theteaching of critical thinking and informal logic by requiring postsecondary institutions to include formal instruction in criticalthinking in their curriculum. According to the order:“Instruction in critical thinking is to be designed to achievean understanding of the relationship of language to logic, whichshould lead to the ability to analyze, criticize, and advocate ideas,to reason inductively and deductively and to reach factual orjudgmental conclusions based on sound inferences drawn fromunambiguous statements of knowledge or belief” (Dumke 1980,Executive Order 338).

The accounts of argument that informal logic and the Critical Thinkingmovement provide are tied to pedagogical attempts to teach studentsand learners how to reason well. One result has been hundreds (perhapsthousands) of introductory textbooks used to teach logic, criticalthinking, and argumentation skills to university and college studentsin Canada, the United States, the United Kingdom, Italy, Poland,Chile, and other countries.

Textbooks in English offer many theoretical and pedagogicalinnovations. Established texts include Battersby 2016 (Is That aFact? A Field Guide for Evaluating Statistical and ScientificInformation, 2nd ed.); Bowell and Kemp 2014 (CriticalThinking: A Concise Guide, 4th ed.); Browne and Keeley 2018(Asking the Right Questions, 12th ed.); Govier 2019 (APractical Study of Argument, 7th ed.); Groarke, Tindale andCarozza 2021 (Good Reasoning Matters!, 7th ed.); Hughes,Lavery and Doran 2014 (Critical Thinking: An Introduction to theBasic Skills, 7th ed.); Seay and Nuccetelli 2012 (How toThink Logically, 2nd ed.); Weston 2018 (A Rulebook forArguments, 5th ed.); and Wilson 2020 (A Guide to GoodReasoning: Cultivating Intellectual Virtues, 2nd ed.).

In Poland, Ajdukiewicz’sPragmatic Logic (1974) is anintroduction to an independently developed “pragmaticlogic” which shares similar goals, teaching and promoting toolsof logic as a central element of a general education. Its applicationaims to ensure that students think clearly and consistently, expresstheir thoughts and ideas systematically and precisely, and justifytheir claims with proper inferences (see Koszowy 2010).

In part because reasoning and argument are ubiquitous and of interestacross many disciplines, informal logic has in many ways beeninfluenced by cognate fields which analyze argumentation in some way.The latter include formal logic, speech communication, rhetoric,linguistics, artificial intelligence, discourse analysis, feminism,semiotics, cognitive psychology, and computational modelling.Considered in this broader context, informal logic is a subfield of abroader multi-disciplinary attempt to develop a comprehensive accountof real life arguing which is commonly called “argumentationtheory.”

Informal logic and argumentation theory have been highlighted atnumerous international conferences hosted by organizations committedto the study of argument. Key conferences include nine Amsterdamconferences (and a tenth conference in Zhenjiang) hosted by theInternational Society for the Study of Argumentation (ISSA); twelveWindsor conferences hosted by the Ontario Society for the Study ofArgumentation (OSSA); six Tokyo Conferences on Argumentation hosted bythe Japanese Debate Association; three meetings of the EuropeanConference on Argumentation (ECA); eight meetings of the InternationalConference on Computational Models of Argument (hosted by COMMA), andmany workshops on issues of argumentation, dialogue, and persuasionorganized by the Polish group ArgDiaP.

1.1 Formal and Informal Logic

One of the driving forces behind the early development of informallogic was a desire for a logic which contained tools of analysis andassessment above and beyond the standard formal methods of the day:propositional logic, truth tables, syllogisms, the predicate calculus,and so on. Johnson emphasizes a “dissatisfaction with formallogic as the vehicle for teaching skill in argument evaluation andargument formation” and a “desire to provide a completetheory of reasoning that goes beyond formal deductive and inductivelogic” (2014, p. 11). Though Ryle never developed a detailedaccount of what he meant by “informal logic,” his commentspoint in a similar direction.

Philosophers and logicians teaching general courses on argument haveoften managed the issues that this raises by mixing formal andinformal methods of analysis. Though the artificial examples ofargument that characterize early editions of Copi (and some othertexts that emphasize formal logic) have been roundly criticized (seeJohnson 1996 and Blair 2015), other authors more successfully meldclassical formal logic and examples of real argument. Harrison 1969 isan example. So are the texts of Pospesel, which contain many examplesof real life reasoning which illustrate the patterns of inferenceassociated with propositional and syllogistic logic (Pospesel andMarans 1978, Rodes and Pospesel 1991, and Pospesel 2002). Little 1980develops an approach to critical thinking and decision making thatintegrates propositional and syllogistic reasoning.

Some informal logicians moved in an opposite direction, developingversions of informal logic that were independent of formal logic,appealing to alternative accounts of argument borrowed from orinfluenced by philosophical reflection, or by other fields that studyargument (notably, rhetoric, dialectics, and speech communication).Toulmin’sThe Uses of Argument (1958) andHamblin’sFallacies (1970) became theoreticaltouchstones for those looking for an informal logic rooted outside offormal logic.

Even in these latter cases, systems and accounts of informal logicshared some core notions with their formal cousins. Mostsignificantly, formal and informal logic assume (i) a premise,inference, and conclusion conception of argument; (ii) the notion thata good argument has premises which are true (or“acceptable”) and a conclusion which follows from them(making the inference the argument depends on “valid” insome way); and (iii) the idea that many arguments can be assessed bytreating them as instances of more generalized forms of argument(“schemes of argument” which include standard deductivepatterns of reasoning).

Today, informal logic is “informal” rather than“formal” primarily because it studies arguments as theyoccur in natural language discourse, and not in formal languages ofthe sort that characterize formal logic. The latter are notable fortheir rigorously defined syntax, semantics, and grammar, and preciselydefined proof procedures. In contrast, arguments as they occur in reallife discourse are notable for their use of everyday language; for themany different norms that apply to them in different contexts; and forthe diverse ways of making meaning (using pictures, facialexpressions, non-verbal sounds, music, etc.) that they employ.

The emphasis that informal logic and its historical precursors placeon natural language argument is in keeping with the social andpedagogical goals that motivate their development. The latter are bestserved by an easily understood, broadly disseminated, understanding ofthe difference between strong and weak instances of real lifeargument. Formal methods (Venn diagrams, probability theory —see Zenker 2013, different kinds of formal logic, etc.) can at timessupport this goal, especially in analyses of particular kinds ofargument, but the overriding aim is natural language discourse guidedby the principles of successful reasoning.

1.2 Argumentation Theory

Argumentation theory is a broad interdisciplinary field that studiesreal life argument. Developments in argumentation theory have beengreatly influenced by formal and informal logic; pragma-dialectics(developed by van Eemeren and Grootendorst and their Dutch or“Amsterdam” school of argumentation); the CriticalThinking Movement; American speech communication; rhetoric;pragmatics; and the Polish School of Argument (which has published arelevantmanifesto). In its attempt to understand argument, argumentation theory does nothesitate to make use of these and other related disciplines: cognitivepsychology, computational modeling, semiotics, discourse analysis, thehistory of art, AI, and so on.

Above and beyond their study of general methods of argument analysis,argumentation theorists investigate arguments in a variety of ways: byexploring particular aspects of arguing (e.g., onus, burden of proof,or the norms that govern arguments in specific contexts); by analyzingarguments from historical, social, political or feminist points ofview; by studying particular kinds of argument (e.g., those expressedin works of art, or those that arise in specific legal contexts); andby investigating the assumptions, conditions (philosophical,epistemological, social, political, institutional, psychological,educational, etc.) which give rise to disagreement, arguing andargument in the first place. In many ways, such endeavors intersectwith informal logic.

Theoretically, argumentation theory incorporates three approaches toargument that have been associated with logic, rhetoric, anddialectics since ancient times. Logic understands an argument as anattempt to justify a conclusion, emphasizing its probative orepistemic merit. Rhetoric treats an argument as an attempt topersuade, emphasizing its persuasive force. Dialectics understands anargument as an element of an exchange between interlocutors withopposing points of view, emphasizing its place in an interactionbetween arguers who argue back and forth.

Like other forms of logic, informal logic emphasizes the epistemicmerit of an argument. That said, its development has been greatlyinfluenced by rhetorical and dialectical considerations, forsuccessful real life arguments must convince their intended audiences(the public, scientists, the Members of Parliament, the readers of aparticular magazine, etc.) and (as Johnson 2000 emphasizes) includeanswers to reasonable objections made by those with opposing points ofview. Bermejo Luque 2011 has proposed a relevant theory of argumentwhich aims to accommodate logical, rhetorical and dialectical pointsof view.

2. Systems of Informal Logic

As Hansen (2012) emphasizes, there are many different methods thatinformal logicians use to analyze instances of argument. An account ofinformal logic needs to make room for the different approaches thisimplies, at the same time that it explains how they constitute ashared field of inquiry. I will attempt to provide such an account byemphasizing systems of informal logic.

I understand an informal logicsystem to be a collection ofprinciples and methods designed for the analysis and assessment ofreal life arguments. Considered from this point of view, informallogic can be described as a field devoted to the creation, study andapplication of systems of informal logic (or, more simply,“informal logics”) and the issues that this raises.

The first textbook that described itself as an informal logic textbookwas Munson’sThe Way of Words: An Informal Logic(1976). As his title emphasizes, his book aims to teach a specificinformal logic (a specific informal logic system) which outlines oneapproach to the analysis and assessment of real life argument. Otherapproaches and other systems are developed in other textbooks and inscholarly discussion.

Different systems of informal logic vary in a number of ways —often, by incorporating formal, rhetorical, dialectical and othermethods of analysis to a greater or lesser extent. Many systemspropose unique approaches or mix methods that they borrow from othersystems. Groarke 2020 has outlined a “BLAST” approach tothe identification and definition of systems of informal logic. Itdefines a specific informal logic systemI, asI ={B,L,A,S,T}, where:

• B = the theoretical background that informsI,
  L = the language used to express the argumentsIanalyzes,
  A = a concept of argument,
  S = a way to “standardize” arguments, and
  T = tools and methods for testing the strength of argumentsevaluated usingI.
  

As I show below, a particular system of informal logic can be definedby outlining and explaining each of its five BLAST elements. When theyhave been defined, different systems of informal logic and theelements they contain can be more precisely compared, contrasted, andevaluated. Historical precursors to present day informal logic can beinvestigated from a similar point of view.

2.1 A Concept of Argument (A)

In many ways, the third element in the BLAST list — a concept ofargument (A) — is the root of all informal logics. Inordinary discourse, the word “argue” can mean “todisagree,” usually with the further implication that someonedoes so aggressively. Informal logics, like other logics, assume anarrower conception of argument (so called “argument-1”),which understands an argument as an attempt to resolve disagreement(or potential disagreement) by providingreasons foraccepting the point of view that it advances.

This notion of argument is “evidentiary” in the sense thatit understands an argument as an attempt to provide evidence insupport of some conclusion. Thepremises in the argumentconvey the evidence which provides those who consider the argumentreasons for accepting the conclusion. As Hitchcock 2007 puts it, anargument is “a claim-reason complex” consisting of (1)premises, (2) a conclusion, and (3) an inference from the premises tothe conclusion (and the implied claim that the conclusion is true,likely true, plausible or should in some other way be accepted).

The following sentence, taken from an article in theHoustonChronicle (Devra Gartenstein 28/01/19) is a simple example ofargument in this sense.

EXAMPLE 1: Small businesses are important because they provideopportunities for entrepreneurs and create meaningful jobs withgreater job satisfaction than positions with larger, traditionalcompanies.

In this example, the word “because” is an inferenceindicator. It tells us that the initial statement in the sentence(“Small businesses are important”) is a conclusion backedby a premise (that small businesses “provideopportunities...”) that provides a reason for believing it to betrue.

The example below is taken from an opinion piece (in theWesternCourier 25/10/08) which criticizes conservative groups opposed toresearch using human embryos.

EXAMPLE 2: This [opposition to embryonic research] is shortsighted andstubborn. The fact is, fetuses are being aborted whether conservativeslike it or not. Post-abortion, the embryos are literally being thrownaway when they could be used in lifesaving medical research.... Livescould be saved and vastly improved if only scientists were allowed touse embryos that are otherwise being tossed in the garbage.

We can summarize the elements of this argument as follows.

Premise: Fetuses are being aborted anyway (whetherconservatives like it or not).
Premise: Lives could be saved and vastly improved ifscientists were allowed to use embryos that are otherwise being tossedin the garbage.
Conclusion: The conservative opposition to embryonic researchis shortsighted and stubborn.

This is another example of a simple argument. In real life arguing,complex arguments may contain tens (or even hundreds) of premises, andare usually made up of layers of inference that proceed from initialpremises to intermediate conclusions which function as premises forfurther conclusions, culminating in a “main” or“principal” conclusion.

All systems of informal logic are attempts to understand and assessarguments in the premise/conclusion sense. In view of this, the corevalue ofA in the BLAST definition is shared by all informallogics, though there are many variations that occur when informallogicians expand this conception by adding other elements to it. Thiscan be done by understanding an argument as a premise-conclusioncomplex which is directed at anaudience, or backed by awarrant, or provided as an answer to anopponent whohas an opposing point of view. When they expand the definition ofargument in these ways, systems of informal logic make an audience,warrant, and/or dialectical context an essential element of a case ofargument.

2.2 Theoretical Background (B)

Other elements recognized in the BLAST definition are notable for theextent to which they vary from one informal logic to another. Thedifferent theoretical backgrounds that inform different systems ofinformal logic (B in the BLAST definition) are of special note,for they reflect the extent to which the development of informal logichas been asearch for new and novel methods of analysis thatcan be applied to real life arguing. In a particular case, this searchmay end in Aristotle, in feminist theories of argument, in rhetoric,in dialogue theory, in speech communication, in formal logic, or insome combination of these and/or other theoretical points of view.

The theoretical background that characterizes systems of informallogic can be used to identify, not only specific systems, but alsofamilies of systems which share key theoretical elements. Manyinformal logicians have, to take one example, turned to fallacy theoryin their attempt to find a logic that can account for real lifearguing. In some cases, the result has been fallacy oriented textbookswhich introduce tens or hundreds of fallacies used to dismiss strawman reasoning, hasty generalizations, slippery slope reasoning, and soon (see, e.g., Bennett 2018).

Systems of informal logic that adopt a fallacy approach can besummarized as instances ofI in whichI = {B,L,A,S,T}, where:B = FallacyTheory, andT = a set of fallacies used to judge instances ofargument. An even narrower set of (“Hamblin”) systems canbe defined as systems in whichB = Hamblin. This is a family ofsystems which is rooted in the account of fallacies proposed inHamblin 1970.

Systems of informal logic that combine fallacy theory with othermethods of testing arguments can be understood as systems which defineT in a way that includes a specific a set of fallacies alongwith other criteria for argument evaluation (e.g., Johnson andBlair’s ARS criteria).

2.3 Language (NL andNL+)

One key element of informal logic is its focus on arguments as theyoccur within natural rather than formal languages.

Initially, informal logic texts defined natural language arguments asverbal arguments: i.e. as arguments expressed and conveyed in wordsassociated with some established natural language. This is animportant focus given that arguments of this sort are a staple in thekinds of arguing that informal logic emphasizes — in letters tothe editor; parliamentary debate; court proceedings; and in essays andbooks written in defense of some point of view (that humans couldcolonize Mars, President Trump was misunderstood, socialism is thebest political system, and so on).

When a system of informal logic is designed to analyze and assessverbal arguments of this sort, the language of argument they assume(L in the BLAST definition) consists of the words and sentences(and the rules governing them) associated with some natural language(“NL”). This makes the language of argument acomplex and nuanced system of meaning which expands the possibilitiesof argument beyond the “informative” statements of factthat authors like Copi took to be the only legitimate realm ofargument. One notable feature of the expanded realm that informallogic studies is the extent to which metaphor and other figures ofspeech are used to support conclusions — something that must beaccounted for in a comprehensive account of informal reasoning.

As the scope of informal logic has expanded to provide a morecomprehensive account of ordinary argument, this verbal paradigm hasfrequently been expanded to make room for real life arguments whichdepend on non-verbal elements. Paradigm examples of these non-verbalelements are photographs, illustrations, drawings, videos, etc. whichare used to provide evidence in support of some conclusion -- as whena photograph or video is used to prove someone’s identity, orproduced in court to give the court areason to believe thatthey were present at the scene of a crime. As Hitchcock (2002) notes,“a poster with a giant photograph of a starving emaciated childand the words ‘make poverty history’ can reasonably beconstrued as an argument.”

Arguments that employ premises and/or conclusions that arguers conveyusing non-verbal visual elements are commonly called“visual” arguments. I leave for elsewhere the questionwhether such arguments are visual in some deeper sense. In most cases,they have verbal as well as visual elements and can, in view of this,be described as arguments which are expressed as an amalgam of verbaland non-verbal (visual) elements.

The two photographs in EXAMPLE 3 (below), taken by the NASA Mars roverPhoenix, were part of a visual argument proposed by the NASAscientists who directed the Phoenix mission. The first photo providesan initial view of a dig made by the rover; the second a view of thesame dig four Martian days (sols) later. When we look at the bottomleft hand corner of the first photograph and compare it to the bottomleft hand corner of the second photograph, we can see white crust inthe first photograph but not the second. According to the NASAscientists, the only way to plausibly explain this change is byunderstanding the crust as water ice which evaporated when the digexposed it to the sun.

EXAMPLE 3

We can summarize the argument as follows.

EXAMPLE 3:
(Visual) Premise: What we see in the bottom left hand cornerof the first photograph of the dig.
(Visual) Premise: What we see in the bottom left hand cornerof the second photograph of the dig.
(Verbal) Premise: The most plausible way to explain thechanges we see (the disappearance of the white crust) is byunderstanding it as water ice.
Conclusion: There is water on the planet Mars.

This argument can be described as visual and verbal. Visual becauseour looking at the photographs andseeing the differencebetween them is a non-verbal component of the argument that provideskey evidence that supports the conclusion. At the same time theargument is verbal because it contains a key verbal component providedby the scientists’ explanation of what we must be seeing. Theconclusion is established by combining these visual and verbalcomponents.

When a system of informal logic recognizes visual arguments of thissort, the value ofL in its BLAST definition can be understoodasNL+, where the+ indicates that the language ofargument includes wordsand non-verbal elements likephotographs and other non-verbal visual images.

One might compare the expansion of informal logic to account forvisual arguments to the attempt to expand the language of formal logic(and, some argue, the notion of argument it embraces) to allow visualdeductions (see Barwise and Etchemendy 1998). Visual premises can beused in geometric proofs, in legal arguments (to proving that someonecommitted a crime, that the murder was heinous, etc.), in reasoningabout planets, stars and black holes, and in aesthetic criticism andevaluation. In ornithology, a well authenticated, clear photograph ofa rare species (say, the Ivory Billed Woodpecker) is widely acceptedas the proper proof that the species is not extinct.

In other cases, a visual image may serve as a conclusion which isbacked by visual and/or verbal premises. A forensic artist concludesthat their drawing of a suspect correctly depicts what they look likeby inferring this from verbal and visual evidence which is provided bythe witnesses they interview.

Kjeldsen 2015 has provided a comprehensive overview of the study of visualarguments. Informal logics that recognize visual arguments do so forthe same reason that they recognize verbal arguments: in order toaccount for the kinds of arguing that play an important role in reallife discourse and exchange. Visual arguments are increasinglysignificant at a time when digital communication facilitates thecreation and distribution of visual images, enhancing and increasingthe use of arguments which employ photographs, videos, art, politicalcartoons, virtual reality, 3D modeling and other kinds of visuals (seeGodden, Palczewski, and Groarke, 2016).

As is the case with words, the images used in visual arguments may, asKjeldsen and other rhetoricians point out, not be intended as literaldepictions of something they represent, but function as visualmetaphors which characterize some situation in an argumentativelycharged way.

The cartoon of Napoleon III below (EXAMPLE 4) appeared inPunch on Feb. 19, 1859.

EXAMPLE 4

This is a clever caricature, but it is something more than a simplecaricature, for the cartoonist uses a drawing of Napoleon-as-porcupineto convey areason to doubt his profession of peace. We mightsummarize his point as the suggestion that Napoleon’s actions --his amassing of the armaments which encircle him like quills on aporcupine -- are not the actions of someone committed to peace. Thedissonance between his actions and his profession of peace invites theviewer to respond to him as they would respond to an actual porcupine-- with caution, concern and suspicion, wary of what he might do withhis weapons (even though he has an “inoffensive” postureand makes an inoffensive sound).

In this case the visual image in the argument is not an attempt toliterally replicate some state of affairs. The core argument we mightextract from the cartoon can be understood as follows.

Premise: Napoleon declares that “The Empire embodiespeace” (“L’Empire c’est la paix”).
Premise: Napoleon has surrounded himself with many armaments.
Conclusion: Napoleon may sound inoffensive when he says that“The Empire embodies peace,” but his build up of armamentssuggests we should be wary of the empire he has built.

This is a visual argument (and the second premise a visual premise) atleast in the sense that it is conveyed visually (and not with thewords in our paraphrase). The verbal paraphrase summarizes theargument, though the non-verbal visual elements the cartoonist usesmust be replicated if we want to exactly replicate their act ofarguing. This is especially important when such arguments are open tocontrary interpretations or have meanings that are difficult to conveyin words.

In the case of thePunch cartoon, we might interpret it in asecond way by adding to our initial paraphrase, understanding theNapoleon III-as-porcupine caricature as an allusion to another famous“Louis” King of France: Louis XII, who ruled from 1498 to1515. Popularly known as the “porcupine” King of France,he adopted the animal as his royal emblem, portraying the Frenchkingdom as a porcupine -- an animal he chose because it was popularlybelieved (to some extent now as well as then) that it could shoot itsquills, symbolizing the offensive and defensive capabilities of theking’s army.

If we understand the cartoonist’s depiction as an allusion toLouis XII, the argument in the cartoon is plausibly assigned anotherpremise that reminds the viewer of the rule of Louis XII, a king whowas famous for rebuilding the French army, which he then employed in aseries of wars against his neighbors (his general strategy iscriticized by Machiavelli inThe Prince). The additionalpremise can be summarized as the suggestion that Napoleon is actinglike Louis XII did — something which provides another reason tobe wary of him.

In many circumstances, the visual elements of an argument (like verbalelements in arguments which are ambiguous or vague) are open tomultiple interpretations. This raises issues of representation andinterpretation. In the Napoleon example, it is difficult to saywhether the cartoonist or his audience understood his depiction to bea reference to Louis XII. In such circumstances, the simplest strategyis one that identifies and evaluates all the plausible interpretationsof an argument.

Visual metaphors are common in works of art, political propaganda, andpolitical cartooning. One popular motif depicts politicians with agrowing Pinocchio nose, suggesting that they are, like the childhoodhero, preposterous liars (see Tseronis and Forceville 2017). In casessuch as this, visual images can have rhetorical as well as logicalsignificance, allowing arguers to convey their arguments inrhetorically powerful ways.

2.4 Modes of Arguing

Informal logicians who advocate for systems of informal logic thatbroaden the language of argument fromNL toNL+sometimes expand the standard notion of argument even further, beyondverbal and visual arguments, to make room for other ways of arguing.

The role of non-verbal carriers of meaning in real life discourseallows many different semiotic modes to contribute to informalarguments. In view of this, some argue that a fully comprehensiveaccount of argument must include a “multimodal” account ofmeaning which recognizes many differentmodes of arguing (seeGroarke 2015). The latter may employ gestures, facial expressions, sounds ofdifferent sorts, tastes, smells, musical notes, and a host of othernon-verbal phenomena.

Groarke 2018, Kišiček 2018, and Eckstein 2018 haveinvestigated “auditory” (or “acoustic”) modesof reasoning that depend on non-verbal sounds. Examples are situationsin which the sound of a siren is pointed to as evidence that thepolice are on their way, or the sound of an automobile engine (or anirregular heart) is the basis of an inference to the conclusion thatit has a leaky valve.

Other modes of arguing invoke the senses in other ways. In 2019, SpaceCargo Unlimited and the University of Bordeaux’s wine institute(the ISVV) sent fourteen bottles of Château Petrus to theInternational Space Station to determine how a year in space wouldaffect their taste and character. A year later, the wine returned toearth where it was analyzed. A key element of this analysis was ablind tasting conducted by 12 professional tasters who compared thewine from space to bottles of the same vintage which had remained onearth. The sommeliers concluded that the wine which had been in spacehad a different, distinct (“more evolved”) taste,inferring their conclusion from their two tastings (which functionedas ‘taste premises’).

Here is another example from a wine tasting.

EXAMPLE 5:

A wine steward attempts to convince a customer that Napa Valley“Frogs Leap PS 2015” is an exceptional Petite Syrah byquoting high praise in a wine guide, and by handing them a glass,inviting them to taste it.

In this case, the steward provides evidence for their claim that FrogsLeap PS 2015 is an exceptional Petite Syrah in two ways: (i) via averbal premise that cites the authority of a wine guide, and (ii) viaa taste test that aims to support this conclusion. In the first case,the result is a verbal appeal to authority, in the second an argumentby taste.

In real life arguing different modes are often mixed. In the case ofverbal arguments, the meaning of oral arguments is often notable forits dependence on the sound of the human voice — which canconvey meaning above and beyond that implied by words. As Gilbert(1997) notes, uttering the sentence “Fine, fine, you’reright, I’m wrong, we’ll do it your way,” “canindicate agreement with what has been said if presented flatly andintended sincerely, or, if accompanied by an expression of anger, canmean that the respondent does not agree at all, but iscapitulating.” (pp. 2–3) Kišiček 2014 hashighlighted the important role that the paralinguistic features oforal arguments play in many instances of verbal argument.

Gilbert 1997 was the first informal logician to suggest that there aredifferent modes of arguing that need to be distinguished. His“multi-modal” theory of “coalescent” argumentaccepts the traditional conception of argument as one mode, adding toit “emotional,” “visceral” (physical) and“kisceral” (intuitive) modes of arguing. He pairs thiswith a very broad account of arguing which understands it as anattempt to resolve conflicting attitudes, beliefs, feelings andintuitions in a way that brings about the “coalescence” ofcompeting points of view.

According to Gilbert’s account, an argument may consist ofsentences and/or expressions of emotion, physical demonstrations anddifficult to define intuitions. This allows a forlorn look or tears tocount as premises in an argument insofar as they provide evidence thatpromotes coalescence (and inference in this broad sense). As Gilbertargues, his non-traditional modes of arguing may, in real lifesituations, provide effective ways of resolving the disagreement thatgives rise to argument.

Gilbert’s account of modes radically expands our understandingof argument beyond “language” as it is traditionallyconceived. In an account of the “anthropology” ofargument, Tindale 2021 defends the alternative “logics”this makes possible. In doing so, he promotes informal logics thatrecognize verbal arguments (and in this senseL) but add to ita much broader range of everyday communication which can convey thesubstance of an argument via expressions of emotion, physical actions(including non-verbal means of communication like so called“body language”), and difficult to define intuitions. Thisexpands the language of argument far beyond words and sentences, in away that maximizes the breadth ofL+.

3. Standardizing Arguments

The ultimate goal of informal logic is normative: i.e. systems oflogic that provide us with tools that can be used to evaluate reallife arguments and the key components they contain. Because real lifediscourse often fails to present the latter clearly, most systems ofinformal logic prepare the way for argument evaluation by explicitlyidentifying an argument’s premises, conclusions, and inferences.The process of doing so is commonly called “standardizing”(S in the BLAST definition).

In the process of standardization, informal logics aim to untangleissues that obscure the structure and content of real life arguments.Arguments in ordinary discourse are, for example, frequently vague,ambiguous or in other ways unclear. Premises and conclusions can beconveyed by rhetorical questions (“Can anyone seriouslybelieve...?” “Could the defendant have been in two placesat once?”) and the key components of an argument may beinterspersed with irrelevant digressions and repetition. When weextract an argument from the context in which it occurs, it can beimportant to recognize what is implicit but relevant at the same timethat we discard what is explicit but irrelevant.

Standardizing clarifies the structure of an argument in ordinarydiscourse by:

• discarding irrelevant and distracting digressions, repetition, andremarks (“noise”) which do not play a role in thereasoning the argument contains;
• restating the content of rhetorical questions and other stylisticdevices that may obscure the meaning of the argument’scomponents;
• clarifying incomplete, vague or ambiguous claims and utterances;and/or
• recognizing components of the argument which are not explicitlyexpressed.

Systems of informal logic may standardize arguments in a variety ofways. In its simplest form, a standardized argument is a list ofpremises and a conclusion (the argument’s inference is theimplicit move from the premises to the conclusion). EXAMPLE 1 abovecan be standardized as follows.

EXAMPLE 1: Small businesses are important because they provideopportunities for entrepreneurs and create meaningful jobs withgreater job satisfaction than positions with larger, traditionalcompanies.

Premise: [Small businesses] provide opportunities forentrepreneurs and create meaningful jobs with greater job satisfactionthan positions with larger, traditional companies.Conclusion:Small businesses are important.

In this example, the word “because” functions as an“inference indicator” which tells us that the claim thatfollows is a premise offered in support of the conclusion whichprecedes it. In other cases, words like “for,”“given that,” “since,” are ways of introducingpremises, while words like “so,” “hence,”“thus,” “therefore,” are used to introduceconclusions.

Verbal inference indicators are an important, but not necessary orsufficient, sign of argument. For indicator words can be used in otherways (“because” may indicate an explanation rather than anargument, a causal connection, emphasis of some sort, a temporalorder, etc.), and are not necessary when a context makes it clear thatsomeone is providing reasons for a conclusion.

3.1 Implicit Premises and Conclusions

One issue that is frequently addressed in standardization is anargument’s dependence on premises and conclusions which areassumed but not explicitly stated.

The following report from the New HampshireRockingham News(30/8/2002) comments on a court case which sent the organizer of dogfights to jail for cruelty to animals.

EXAMPLE 6: A co-ordinator for the Humane Society supported a prisonsentence, claiming that the minor penalties normally associated withmisdemeanor convictions are not a sufficient deterrent in thiscase.

We can standardize the co-ordinator’s argument as follows.

Premise: The minor penalties normally associated withmisdemeanor convictions are not a sufficient deterrent in this case.
Implicit Premise 1: Penalties for crimes should have adeterrent effect.
Implicit Premise 2: Prison is a sufficient deterrent.
Conclusion: A prison sentence, but not the minor penaltiesnormally associated with misdemeanor convictions, is appropriate.

It is important to recognize the assumption which is rendered asImplicit Premise 1 (which is, in Toulmin’s words,“a warrant”) for it is a claim that the argument dependson when the arguer concludes that the penalties normally associatedwith misdemeanors are not a sufficient deterrent in this case. Theremaining part of the conclusion — the suggestion that a prisonsentence is appropriate — depends onImplicit Premise2, which recognizes the further assumption that this will have adeterrent effect.

Recognizing the argument’s implicit premises prepares the wayfor argument evaluation, for they, like the argument’s explicitpremise, need to be evaluated when the argument is assessed. If wereject the implicit premises (by, e.g., arguing that the goal ofcriminal penalties should be retribution, not deterrence), then theargument fails to provide convincing evidence for its conclusion.

Arguments with implicit premises or conclusions are recognized inancient discussions ofenthymemes: syllogisms with unstatedpremises. A contemporary example is American Vice-President DickCheney’s defense of the Bush administration’s decision notto try foreigners charged with terrorism offenses as prisoners of war(something that would guarantee legal protections for those accused ofterrorism).

EXAMPLE 7 (from a report in theNew York Times, 15/11/2001):
“The basic proposition here is that somebody who comes into theUnited States of America illegally ... is not a lawful combatant....They don’t [therefore] deserve to be treated as a prisoner ofwar.”

We can standardize the argument as:

EXAMPLE 8:
Premise: Somebody who comes into the United States of Americaillegally ... is not a lawful combatant.
Implicit Premise: Someone who is not a lawful combatantdoesn’t deserve to be treated as a prisoner of war.
Conclusion: They don’t deserve to be treated as aprisoner of war.

As in many other cases, the argument’s implicit premiseidentifies the link that ties the explicit premise to the conclusion.When we evaluate the argument, it raises a number of questions. Howshould a “lawful combatant” be defined? Why are combatantswho illegally enter a country for the purpose of war (in undertakingsurveillance or going behind enemy lines) widely recognized asprisoners of war? What are our moral obligations to combatants, lawfuland unlawful?

In other enthymemes, the conclusion of an argument may be unstated. Ina debate over the question whether witnesses to a crime can betrusted, an arguer might state: “They are friends ofthe accused, and no friends of the accused can be trusted.” Suchclaims clearly suggest that “They cannot betrusted,” a claim that needs to be recognized as an implicitconclusion in an attempt to standardize and evaluate the argument.

As in the case of verbal arguments, implicit premises and conclusionsplay an important role in many visual and multimodal arguments. InEXAMPLE 9 (below), the title “Just Add Vodka” issuperimposed over a gigantic bottle of vodka pouring its contents onthe scene below. Outside the vodka splash, one sees a sleepy hamlet.Inside the vodka splash, it is transformed into a bustling cityscapewhich boasts skyscrapers and a nightlife with lights, people,nightclubs, bars, and restaurants.

EXAMPLE 9

The image in this advertisement is a visual metaphor which suggeststhat vodka can transform one’s life in the way that ittransforms the scene in the advertisement, turning the (dreary) lifeone lives in a sleepy hamlet into the kind of exciting nightlife onefinds in a cosmopolitan urban center. Insofar as this message isfeatured in an advertisement, we can plausibly understand this messageas a proposedreason to buy the vodka in question.

We might standardize the argument this implies as follows.

EXAMPLE 9:
(Visual) Premise: If you drink our vodka, it can transformyour night life in the way it transforms the village in thephotograph: into an exciting major city.
Implicit Premise: A life of urban excitement is preferable tothe quiet life of a village.
Conclusion: You should “Just Add Vodka” to yourlife.

I have summarized the first premise in the argument in a way thatrefers to the image because it is difficult to fully capture the(almost magical) transformation the advertisement promises if we tryto translate it into words. The implicit premise in thestandardization is a key part of the argument because it is a keyassumption made in the move from the (visually) explicit premise tothe conclusion. So understood the argument can be analyzed andevaluated as an argument which has a questionable explicit andimplicit premise (and an inference which is an instance of the fallacy“Affirming the Consequent”).

The attempt to identify implicit premises or conclusions in anargument can raise some significant theoretical questions when it isstandardized. All arguments rely on many assumptions, raising thequestion whether and when and how they should be recognized. In casesin which it is clear that an unstated premise or conclusion needs tobe recognized, it can often be interpreted in different ways.

One principle that many systems of informal logic use to choosebetween alternative interpretations of implicit argument components isthe “Principle of Charity.” It favors an interpretation ofan argument which makes it as credible as possible. In manysituations, this can best be accomplished by attributing it a“logical minimum,” understood as the weakest implicitcomponent needed to successfully connect the argument’s premisesto its conclusion.

3.2 Key Component Tables and Diagrams

Standardizing arguments by listing their premises and conclusions isone way to delineate the content of an argument and prepare it forevaluation. But standardizing of this sort has a major shortcoming,for it does not distinguish between different kinds of inferences anargument may contain. One way to address the issues that this raisesis by standardizing an argument with a table that catalogues anargument’s premises and conclusions (a Key Component or“KC” table) and combining it with an argument diagram (a“mapping”) that depicts the structure of its inferences.

In EXAMPLE 10 (below), I have used this method to standardize anargument that Kretzmann uses in his account of the medievalphilosopher William of Sherwood, where he concludes that it is likelythat William was a Master at the University of Paris. The first columnof the KC table lists the premises and conclusion of the argument; thesecond assigns them their role as premise or conclusion; the thirdlists the source from which they are derived. The diagram that followsdepicts the relationships between the argument’s key components,using arrows to indicate the inferences it includes.

EXAMPLE 10

This standardization shows that the Sherwood argument is supported bythree “convergent” premises which provide threeindependent reasons that support the argument’s conclusion indifferent ways.

In other instances of argument, two or more “linked”premises combine to support a conclusion with a single inference. Theargument “The murderer was very strong, so George cannot be themurderer.” is an enthymeme which assumes that “George isnot very strong.” Using square brackets ([ ]) to indicate thisimplicit component, we can standardize the argument with the followingKC table and diagram. In this case, the linked premises are indicatedwith a plus sign (“+”) that connects them in the diagram.It indicates that they support a conclusion (only) when combined.

EXAMPLE 11

The use of KC tables and diagrams is not limited to purely verbalarguments. When arguments have non-verbal key components, visual andmultimodal premises and conclusions can be recognized in a keycomponent table by ostension, or by reproducing them in some way. Oncethey are identified in a KC table, the inferences such argumentsdepend on can be mapped in standard ways.

The following table and diagram standardizes EXAMPLE 3, which containsan inference from three linked premises (two visual and one verbal) tothe conclusion that there is water on the planet Mars.

KC table are not the only way to diagram the structure of real lifearguments. Diagramming (mapping) has its own history, whichincorporates many different ways of diagramming arguments. Theusefulness of diagramming is already recognized in Whately 1826 and,in the early twentieth century, in Wigmore 1913, who develops a formof mapping (“evidence charts”) designed to portray andanalyze complex chains of judicial reasoning.

The development of informal logic has kindled a renewed interest indifferent kinds of diagrams which are supported by the development ofassociated software (Rationale, Reason!Able, Araucaria, Athena,Compendium, Theseus) and online aids (Debate Mapper, TruthMapping.Com,Argunet, Agora).

3.3 Supplemented Diagrams

KC tables and diagrams prepare the way for argument evaluation byclarifying the internal structure and content of an argument. Otheraspects of an argument that may need to be considered in argumentassessment can be included in a “supplemented” diagramwhich adds an account of the context in which it is embedded. Threeaspects of arguments merit note in this regard.

The first is theaudience to which an argument is addressed.Most real life arguments are used in an attempt to convince someintended audience of some point of view. In view of this, successfularguments must be built with this in mind.

A convincing argument for the conclusion that the United Nationscannot be trusted must address different issues when it is directed ata Chinese, Norwegian, Kenyan, Israeli, Swiss, Palestinian, etc.audience. As rhetoric has emphasized since its beginnings, this meansthat successful arguers must construct their arguments in ways thatrecognize the beliefs, attitudes and values of their intended audience(and in this sense ‘speak’ to them). Tindale (1999, 2004,2010) has imported this notion into informal logic, advocating aninformal logic that incorporates an analysis of audience.

A second contextual factor relevant to the evaluation of an argumentis the goal of the arguer. As Hitchcock 2002 points out, acts ofarguing may make a declaration (“The evidence shows that youcommitted an assault, so I find you guilty as charged.”);command or make a request (“You were there, so you must tell uswhat happened.” “The children are shivering, so pleaseclose the door.”); make a promise (“I know it matters toyou, so I promise to go tomorrow.”); express a sentiment(“What we did was inexcusable, so we beg yourforgiveness”); and function in many other ways.

As Pinto and Gilbert have emphasized, this means that a successfulargument (which is successful in the sense that it accomplishes thearguer’s purpose in presenting the argument), may produce awithholding of assent (or full assent) to some proposition, aparticular attitude, an emotional state like fear or hope, or acertain kind of behavior (by, e.g., as when an argument demands thatpeople take up arms against a foe or take action in support of socialchange). When one bargains, the goal of argument is not truth, but abargain that serves one’s interests. As Hoffman 2016 notes, anargument may not aim to resolve disagreement, but to promotereflection and the raising of important questions.

The different goals arguer’s try to achieve via argument maymake their success and legitimacy turn on norms and rules that add to(or subtract from) the traditional strictures that guide argumentevaluation. In some circumstances, it makes ultimatums, exaggerations,threats and insults a permissible element of arguing. In sharpcontrast, they are unacceptable in attempts to determine what is truefrom a scientific point of view, where such behaviors are instances ofthe fallacyad baculum.

Walton 2007 accommodates the different goals associated with real lifearguments by distinguishing between different kinds ofdialogues in which arguing occurs. The rules for a particularkind of dialogue define what types of argumentative moves are allowed,what kinds of questions and responses are permitted, and what normsarguments must adhere to.

The seven basic types of dialogue he distinguishes can be summarizedas follows.

In dialogues of inquiry, arguments are used as tools in an attempt toestablish what is true. So understood, arguments must adhere to strictstandards that determine what counts as evidence and counter-evidencefor some point of view. In eristic dialogue, arguing is combat and theaim is to vanquish one’s opponent (and humiliate them, ideallyby wowing one’s audience with one’s mental gymnastics). Indoing so, sophistical tricks and fallacious reasoning are welcome ifthey serve this end.

Walton’s dialogue typology leaves room for more narrowly definedkinds of dialogue. Collective bargaining is a specific kind ofnegotiation dialogue which is governed by legal rules and wellestablished practices that very precisely delineate what is and is notallowed in bargaining. Different subdialogues are associated withdifferent norms, rules and practices.

A third contextual factor that may warrant comment in a supplementeddiagram is the dialectical context in which an argument occurs. In hisaccount of argument, Johnson 2000 distinguishes between the“illative” core of an argument and the argument’s“dialectical tier,” understanding the former as a“proto-argument” which consists of a set of premisesoffered in support of some conclusion. It is the kernel of anargument, but he considers it an argument in the full sense only if itfully engages the dialectical tier, considering alternative points ofview, addressing objections to the conclusion it proposes.

4. Testing Arguments

The ultimate goal of informal logic is normative: an account ofargument and systems of informal logic that can be used to determinewhen and whether real life arguments are strong or weak, good or bad,convincing or unconvincing. Standardizing prepares arguments for suchassessment. This makesT in the BLAST definition — thetools and methods which are used to test argument strength — themost important defining element in a system of informal logic.

Almost all informal logics understand a good (strong) argument to bean argument with “acceptable” premises and a“valid” inference — i.e. a conclusion that followsfrom them. Hansen 2012 has argued that informal logic should followclassical logic, and not concern itself with the assessment of premiseacceptability, but its engagement with real life arguments (and thedesire to evaluate them in a fulsome way) has produced a field thatincludes this within argument evaluation. In this and in otherregards, systems of informal logic adopt many different approaches toargument assessment.

4.1 AV Criteria

In classical logic, an argument is (deductively) valid if it isimpossible for its premises to be true and its conclusion false. Onthis account, the ultimate aim of arguing is a “sound”argument: i.e. a valid argument with true premises.

Within informal logic, the simplest criterion for good arguments is aninformal analogue of soundness. It understands a good argument to bean argument that justifies its conclusion by providing good (strong,credible, etc.) reasons for believing it. Within the argument, thisimplies premises which are “acceptable” and a conclusionthat follows from them. We can summarize this basic criterion asT = {A,V}, whereA is an account ofpremise acceptability, andV is an account of informal validitywhich determines when a conclusion follows from premises in a way thatis approved of (deductively, inductively, conductively, and/orabductively, etc.).

Following Johnson and Blair (1977, 1994), many systems of informallogic adopt anARS version of theseAV criteria, making“Acceptability, Relevance and Sufficiency” therequirements for good argument. On this account, premises areacceptable when they are true or acceptable in some other way;relevant when they provide some (i.e. any) support for the conclusionof the argument; and sufficient when they provide enough support towarrant its acceptance — as likely, true, plausible, etc.

Premise Acceptability

Within informal arguments, premises may be acceptable in a variety ofways. In many circumstances, they are acceptable if they are likelytrue and unacceptable if likely false.

It is worth noting that this truth criterion can be expanded to applyto visual premises. An image functioning as a visual premise may, forexample, be evaluated as a “true” or “false”depiction of what it represents. A photograph or an image may beunacceptable because it is untrustworthy or categorizes a situation ina misleading way. Photographs are often ‘doctored’ or inother ways designed to present things in ways that do not accuratelyreflect what is photographed. Other kinds of multimodal premises canbe understood as likely true to the extent that they are a reliablebasis for an inference.

In some kinds of dialogue — in the exchanges that characterizenegotiation, bargaining, eristic, and persuasion — acceptablepremises may not need to be true. In bargaining(“haggling”) a buyer may claim that “I will not giveyou a penny more than $300 for that lamp” as a premise insupport of the conclusion that the seller should agree to a lowerprice. This counts as an acceptable premise even if it is an idlethreat that the buyer will never carry out, for threats of this sortare an acceptable element of the arguments that take place in thiskind of dialogue.

In other cases, informal logics use acceptability rather than truth asa criterion for judging premises in contexts in which it is difficultto judge premises as true or false. In such cases, acceptable premisesmay be plausible (or exploratory) hypotheses, claims that can only besaid to be generally accepted or assumed, or ethical or aestheticjudgments which are not easily categorized as true or false.

In still other circumstances, truth may be required for acceptability,but only one of a number of conditions that must be satisfied. Evenwhen a premise is true, it may be unacceptable because it violates therules of interaction that govern the dialogue in which it is embedded.In a legal proceeding or a formal hearing, premises and arguments mustnot entertain premises that violate rules of procedure.

In situations in which arguments are attempts to convince a specificaudience of a conclusion, an acceptable premise may need to be true,but also acceptable to the members of this audience. As Aristotlesuggests in theRhetoric, successful arguments may need tohave premises that are in keeping with thepathos of anaudience (and do so in a way that does not undermine the character— theethos — of the arguer). As Gilbert 1997,2014 has emphasized, there are many real life circumstances in whichthe emotional acceptability of a premise is required for argumentsuccess.

One of the first VR productions by theNew York Times was“Kiya,” a production which recreated an incidence ofdomestic abuse in an attempt to provide support for the importance ofattempts to address issues of domestic violence. Its producerdescribes it as an attempt to use “the immersive power ofvirtual reality: its ability to generate intense empathy on the partof the viewer; to wring from the audience the intense emotionalconnection that these stories deserve” (NYT, Jan 21, 2016).

Inference Validity

In its attempt to account for a broad range of real life arguing,informal logics have expanded traditional notions of premiseacceptability. Something similar has happened in the case of inferencevalidity. The end result is an expansion of both sides of theAV criteria for good argument.

In the case of inference validity, this expansion has beenaccomplished by treating deductive validity as one variant ofvalidity, and by recognizing other “defeasible,”non-deductive ways in which premises may entail conclusions. Govier1987 dubs the deductive/inductive distinction as “the greatdivide,” emphasizing the latter over the former. Sometimesinformal logic systems understand inductive arguments narrowly, asinductive generalizations. Sometimes more broadly, as arguments whichhave premises that imply that a conclusion is (only) probable orplausible, leaving open the possibility that it is false.

“Conductive” arguments support their conclusions byaccumulating non-decisive reasons in their favor. They are valid whenthey collect enough reasons to warrant their conclusions. In aparticular case, different elements of evidence may suggest but notprove that someone charged with murder is guilty but make theconclusion likely if enough evidence of this sort is accumulated (awitness claims he pulled the trigger, the ballistics report shows thatthe bullet came from a gun he owned, he wrote an e-mail saying hewould “get” the victim, etc.).

Strong “abductive” arguments are convincing instances of“inference to the best explanation” (see Harman 1965).They recognize some facts, point out that they are entailed by somehypothesis, and conclude that the hypothesis is true. Taken at facevalue, abductive arguments appear to be instances of the deductivefallacy “affirming the consequent,” but play an importantrole to play in medical, scientific and legal inquiry (see Walton2004).

4.2 Fallacy Theory

AV criteria are in many ways an extension of the notion of goodargument enshrined in classical logic. In the search for ways to dealwith real life arguments, some informal logicians have moved in adifferent direction, reviving fallacy theory as an alternative.Hamblin 1970 has become a touchstone for moves in this direction.

Systems of informal logic that rely on fallacies test arguments byasking whether their proponents are guilty of fallacious reasoning.While there is no agreed-upon taxonomy of fallacies, many canonicalfallacies have been emphasized in the analysis of informal arguments.They include formal fallacies like affirming the consequent anddenying the antecedent; and informal fallacies likeadhominem (“against the person”), slippery slope,ad baculum (“appeal to threat or force”),admisericordiam (“appeal to pity”), “hastygeneralization,” and “two wrongs” reasoning (as in“two wrongs don’t make a right”). The systems ofinformal logic taught in textbooks often add specialized variants ofthe standard fallacies (“misleading vividness” designatesthe misuse of vivid anecdotal evidence in hasty generalizations, andso on.)

Woods and Walton 1982 and Hansen and Pinto 1995 contain detaileddiscussions of the definition, analysis and assessment of fallacies.In argumentation theory, van Eemeren and Grootendorst 1992 propose a“pragma-dialectical” account of fallacies which treatsthem as violations of rules that govern critical discussion --dialogues that attempt to resolve a difference of opinion. Battersbyand Bailin 2011 view fallacies as patterns of argument patterns“whose persuasive power greatly exceeds its probative [i.e.evidential] value,” making fallacies errors in reasoning thatordinary arguers are attracted to in view of their rhetorical appeal.

Some fallacies — e.g., equivocation and begging the question(i.e. circular reasoning) — highlight important issues thatfrequently interfere with real life arguing, but fallacy theory hasbeen criticized when it is adopted as a general account of argument.The issues this raises include its unsystematic nature, disagreementsabout the definition and nature of specific fallacies, and theemphasis that fallacy theory places on faulty reasoning rather thangood argument. Hitchcock (1995, 324) writes that the idea that weshould teach reasoning by fallacies is “like saying that thebest way to teach somebody to play tennis without making the commonmistakes is to demonstrate these faults in action and get him to labeland respond to them” (see Feldman 2009).

The theoretical issues raised by fallacy theory are compounded byinstances of traditional fallacies which have a reasonable role toplay in real life arguing. Appeals to pity and other appeals toemotion have, to take one example, a legitimate role to play in moral,political and aesthetic debate. The following examples highlight othercircumstances in which arguments which fit the definition of atraditional fallacy cannot be so readily dismissed.

EXAMPLE 12:
A remark from a Danish television debate over the question whether theDanish church should be separated from the Danish state (Jorgensen1995, 369): “You should not listen to my opponent. He wants tosever the Danish church from the state for his own personalsake.” This seems a classic example ofad hominem,Kahane 1995 (p. 65), describing it as a fallacy that occurs when anarguer attacks “his opponent rather than his opponent’sevidence and arguments.” But this is an accusation of conflictof interest which cannot be dismissed out of hand. If there is reasonto believe that an arguer favors a point of view because they havesomething to gain from it (say, the purchase of a company in whichthey own shares), this does raise questions about the extent to whichtheir arguments should be entertained.

EXAMPLE 13:
Martin Luther King Jr., influenced by Gandhi, argued that one canjustifiably break laws in a struggle for social justice. Sucharguments play a central role in the civil rights movement. Theycannot be summarily dismissed, though they appear to be clear cases of“two wrongs make a right.”

EXAMPLE 14:
The argument that “the attempt to use military force to put anend to terrorism is wrong because it will take us down a slipperyslope that will end in improper interference in the affairs ofindependent states” cannot be dismissed because it is aninstance of slippery slope reasoning. If it is true that some actionwill precipitate a chain of consequences that lead down an allegedslippery slope, this is a good reason to question it.

Examples of this sort have forced careful accounts of fallacies tomake room for reasonable arguments which share the form of traditionalfallacies.

In doing so, it is helpful to distinguish between fallacies which doand do not have non-fallacious instances. Equivocation,post hocergo propter hoc,non sequitor and hasty generalizationare commonly classified as forms of argument that are inherentlymistaken. In contrast, traditional fallacies likead hominem,two wrongs reasoning, guilt by association, and appeal to pity arepatterns of reasoning which can, when they are constructed in theright way, play a legitimate role within real life reasoning (and are,in view of this, sometimes treated as argument schemes rather thanfallacies).

4.3 Natural Language Deductivism

Natural Language Deductivism (“NLD”) is an approach toinformal reasoning that retains classical logic’s focus ondeductive validity (see Groarke 1999, andGovier 1987, who develops an initial account NLD, but ultimately favors a moreradical break from classical logic). It suggests that we shouldinterpret informal arguments as attempts to create deductively validinferences which can be analyzed and assessed accordingly. In adeductivist system of informal logic, theV in theAVcriteria for good arguments is this classical notion of validity.

NLD has frequently been rejected on the basis of the common, butmistaken, notion that deductively valid arguments must have certainconclusions — a misconception that seems founded on deductivevalidity’s historical connections to formal logic andmathematics (see Groarke 1999). It is true that ordinary arguingrarely satisfies the strict proof procedures they imply, but deductivevalidity is not restricted to this compass and there are manyinstances of ordinary argument which are clear examples of deductivelyvalid argument.

In cases of deductive reasoning, the conclusion of an argument neednot be certain, but only as certain as the premises, creating ample roomfor conclusions which are merely likely, plausible, or probable.EXAMPLE 15 is taken from a radio commentary on population growth.

EXAMPLE 15:
The population of the world will grow from 6 to 9 billion in the nextfifteen years so we will, if we are to provide sufficient food foreveryone, need to find a way to provide food for an additional 3billion people.

In this case, the premise of the argument is not certain, butreasonably thought to be true — because it was (in thecommentary) backed by an extrapolation from well establishedpopulation trends. The deductively valid inference based upon it makesit reasonable to judge the conclusion of the argument true as well,though it is not certain, as all predictions about population growthare, at best, plausible conjectures.

NLD’s plausibility as a general theory of argument turns on itsaccount of arguments which are not prima facie deductive. Faced witharguments of this sort, it preserves the deductivist approach byattributing an implicit premise (essentially, a deductive warrant) tosuch arguments in a way that deductively connects an argument’spremises to its conclusion. Typically this is an“associated” conditional of the form “If P, thenC” where P is the argument’s premises and C is itsconclusion.

A 2015 blog by a professional dietician (Dr. Cristina Sutter)criticizes arguments that justify the claim that garcinia cambogia isa miracle weight loss pill by appealing to the authority of thepopular television personality “Dr. Oz.” — instancesof the reasoning “Dr. Oz Says It, So It Must Be True.” Wecan standardize the pattern of argument she criticizes as:

EXAMPLE 16:
Premise: Dr. Oz says [that gracinia cambogia is a miracleweight loss pill].
Conclusion: This must be true.

If one judges only by the explicit premise in this argument(“Dr. Oz says...”), this is not a deductively validargument, for it is obvious that the premise could be true and theconclusion false: Dr. Oz could say gracinia cambogia is a miracleweight loss pill and be wrong. That said, anyone using this argumentmust assume an associated conditional which can be understood as animplicit premise, allowing us to standardize the argument as:

Premise: Dr. Oz says [that gracinia cambogia is a miracleweight loss pill].
Implicit Premise: If Dr. Oz says this, it must be true.
Conclusion: This must be true.

So understood, the Dr. Oz argument is deductively valid, but notsound, as it is a valid argument with a problematic implicit premise.

NLD deals with inductive generalizations in a similar way. Considerthe following example from a conversation about French men.

EXAMPLE 17:
“French men are fastidious about their appearance. I have workedwith many and this was what I found.”

In this example, the move from the premise to the conclusion of theargument assumes that the sample of French men the arguer is familiarwith are a representative sample of French men. If this is not likely,then the sample does not provide good reasons for concluding thatFrench men are, in general, as fastidious if they are. If we recognizethis assumption as an implicit premise when we standardize theargument, then the argument is deductively valid, for a representativesample is a subset of a population that accurately reflects thecharacteristics of the larger group.

In this way, NLD turns the uncertainty that characterizes inductivegeneralizations (and other forms of informal validity) intouncertainty that is connected to an associated conditional whichwarrants the move from an argument’s premises to its conclusion.This does not eliminate such uncertainty, but maintains it as a keyconsideration in argument evaluation, for it makes the status of thiswarrant an essential element of premise acceptability.

In favor of NLD, it has been argued that reconstruction of manyarguments it proposes is a dialectically useful way to make explicitthe key assumptions that arguments depend on, and frees us from theneed to distinguish between different kinds of validity in ways thatcan be problematic when they are applied to real life arguing. Thepragma-dialectical account of indirect speech acts (Eemeren andGrootendorst 2002, Groarke 1999) provides a way to reconstructarguments as deductive arguments when NLD requires it, though Johnson2000 and Godden 2004 argue that NLD is an artificial theory whichforces informal arguments to adhere to an overly restrictive model ofinference.

4.4 Argument Schemes

Argument (or “argumentation”) schemes are recurringpatterns of reasoning. Once identified they can be used to evaluate anargument which is instance of a scheme, or as a template or recipearguers can use when they construct an argument which is an instanceof a scheme. Walton, Reed and Macagno 2008 provide a compendium of 96schemes. Wageman has developed a Periodic Table of Arguments which provides a systematized account of basic schemes.

Rules of inference likemodus ponens andmodustollens can be understood as deductive schemes. Other schemescommonly used in ordinary arguing include Argument by Sign, Argumentby Analogy, Argument by Example, and Slippery Slope Reasoning. Dove2016 and Groarke 2019 have shown how visual arguments with non-verbalvisual elements may be instances of common schemes, and haveidentified some schemes which are inherently visual.

The most common approach to argument schemes combines a pattern ofargument with a set of “critical questions” with which itis associated. The schemeArgument from Authority(“Appeal to Authority,” “Appeal to ExpertOpinion”) and the critical questions it raises can be formalizedas follows.

A is an authority in domain D.
A says that T is true.
T is within D.
(Therefore) T is true.

Critical questions:
1. How credible is A?
2. Is A an authority in domain D?
3. What did A assert that implies T?
4. Is A someone who can be trusted?
5. Is T consistent with what other experts assert?
6. Is A’s assertion of T based on evidence?

Prakken 2010b understands argument schemes as inference rules, somecritical questions ensuring the truth of an argument’s premises,others ensuring that the context of the inference is appropriate.

Another approach to schemes builds the answers to critical questionsinto a ‘full’ definition of the scheme, treating them asrequired premises in convincing instances of the scheme. Taking thisapproach, the schemeArgument from Authority can be definedas follows.

A is a credible authority in the domain D.
A asserted X, which implies T.
A can be trusted and T is within domain D.
T is consistent with what other experts in domain D assert.
A’s assertion of T is based on evidence.
(Therefore) T is true.

The critical question approach to schemes suggests that a credibleargument from authority must include acceptable premises of the formoutlined in the definition of the scheme, and is valid if it is backedby answers to the scheme’s critical questions. Taking the‘full’ approach, a valid argument from authority mustinclude the premises that define it as as a good argument as explicit(or possibly implicit) premises. In both cases, the result is anaccount of premise acceptability and validity which is tailored tospecifically apply to arguments from authority.

Different argument schemes are a refinement of generalAVcriteria, creating specific criteria which can be applied to differentkinds of argument.

When a student essay claims that “we should not stockpilenuclear weapons” because Einstein told us that this would lead“to destruction even more terrible than the present destructionof life” (EXAMPLE 18), this is an appeal to authority whichinvokes Einstein as an authority. In order for it to be a convincingargument from authority, it would need to fully satisfy the conditionsoutlined in our definition of the schemeArgument fromAuthority.

The attempt to satisfy the requirements this implies produces aversion of the argument which can be summarized as follows.

EXAMPLE 18 expanded to satisfy the criteria for a convincing argumentfrom authority:
1. Einstein (A) is a credible authority on nuclear weapons (D).
2. Einstein (A) asserted that the stockpiling of nuclear weapons wouldprecipitate “destruction even more terrible than the presentdestruction of life” (X), which implies that we should notstockpile nuclear weapons (T).
3. Einstein (A) can be trusted and questions about stockpiling nuclearweapons (T) are questions about nuclear weapons (D).
4. The claim that we should not stockpile nuclear weapons (T) isconsistent with what other experts on nuclear weapons (D) assert.
5. Einstein’s (A’s) assertion that we should not stockpilenuclear weapons (T) is based on evidence.
6. (Therefore) We should not stockpile nuclear weapons (T).

This attempt to satisfy the conditions for a good instance of argumentfrom authority fails because it produces a number of problematicpremises. Other experts disagreed (and continue to disagree) withEinstein’s suggestion that it is a mistake to stockpile nuclearweapons. More fundamentally, the proposed argument is founded on tooloose an account of nuclear weapons as a domain of expertise. Einsteinis a renowned expert on nuclear physics but this it does not make himan expert onthe social and political issues raised bynuclear weapons. This is something that a convincing version of theargument would have to establish.

In some ways, the scheme approach to argument assessment rectifiesproblems that arise in systems of informal logic that adopt thefallacy approach to argument evaluation. For traditional fallacieswhich have non-fallacious instances can be understood, not asfallacies, but as argumentation schemes which are legitimate forms ofreasoning when they are properly employed. Fallacy definitions can beturned into scheme definitions by identifying a list of criticalquestions (or required premises) that specify what is required to makethe arguments in question valid.

Ad hominem is a case in point, for there are many instancesin which criticisms of an arguer (rather than their position) are areasonable way to cast doubt on their views. We can specify when thisis so by listing critical questions that determine whether this is soin a particular case of argument. The basic question that must beasked is whether there is a good reason why the arguer’s viewsshould not be taken seriously — a question that subsumes themore specific questions whether they have repeatedly shown poorjudgment, are biased, lack expertise in the area in question, or arefor some other reason an arguer who should not be listened to.

Treated in this way,ad hominem is a legitimate scheme ofargument, but there are (as there are in the case of all schemes) manysituations in whichad hominem arguments are poor instancesof the scheme. In this and many other cases, traditional fallacies canbe regarded as deviations from an inherently correct scheme ofreasoning.

4.5 Testing Systems

Most informal logics combine different ways of evaluating arguments.In this way,T in a particular system tends to be some combinedset of tools that can be used in this endeavor. In most cases,T = {F,AV,AS}, whereF is somelist of fallacies,AV is some kind ofAV criteria (say,the standardARS criteria) andAS is some set ofargumentation schemes.

But systems of informal logic can accommodate other, less commoncriteria for deciding whether arguments are good or bad, strong orweak. A system might, for example, incorporate criteria which arefounded on a virtue-based approach to argument (seeVirtues and Arguments), on feminist principles, or on notions derived from rhetoric, theoriesof communication, or other cognate fields.

5. Informal Logic Within A Broader Context

Informal logic’s attempt to understand argument as it occurs ina broad range of real life situations continues to evolve in a waythat is influenced by the study of real life reasoning that takesplace within the broader scope of argumentation theory.

One cognate field of note is Artificial Intelligence (AI). It relieson step by step accounts of informal reasoning in a wide array ofcontexts. Informal logics provide this in a general way that hasinfluenced the attempt to model argumentation between agents inmulti-agent systems which mimic or assist human reasoning.Computational models have been applied to large-scale collections(‘webs’) of inter-connected arguments, and to reasoningabout medical decisions, legal issues, chemical properties and othercomplex systems. Automated argument assistance functions as acomputational aid that can assist in the construction of an argument.Verheij 2014 provides an overview of the issues that this raises.

The development in the empirical study of real life reasoning is thestudy of argument “corpora” — large collections ofargument drawn from natural language discourse. In an early study ofthis sort, Jorgenson, Kock and Rorbech 1991 analyzed a series of 37one-hour televised debates from Danish public TV. The debates featuredwell-known public figures arguing for and against policy proposals. Arepresentative audience of 100 voters voted before and after thedebate. Their conclusions were compared with standard notions of“proper” and “valid” argumentation. Otherstudies consider corpora made up of large databases of selectedwritten texts (see, e.g., Goodwin and Cortes 2010, and Mochales andIeven 2009).

Argument mining is a subfield of data mining, or text mining (andcomputational linguistics). It uses software and algorithms thatautomatically process texts looking for argument structures —for premises, conclusions, argumentation schemes, and extended webs ofargument. The texts studied include legal documents , on-line debates,product reviews, academic literature, user comments on proposedregulations, newspaper articles and court cases, as well as dialogicaldomains.ARG-tech, the Centre for Argument Technology, has played a central role instudies of this sort.

Other research relevant to informal logic has highlighted many ways inwhich the success of real life arguments depends on aspects ofargumentation which are not well integrated into standard systems ofinformal logic. The latter include an arguer’s ability to drawattention to their argument (using “argument flags” thatattract the attention of an intended audience); their personalcredibility,ethos, or standing; or their ability to situatetheir argument within a broader context of debate or dialogue. Thestudy of these and other pragmatic, social, dialectical, semiotic andrhetorical features of arguing will probably play a role in thecontinued development of informal logic.

The expansion of informal logic to account for an ever broader rangeof argument is evident in discussions of the use of narratives withinargument. In Plato’sRepublic, Glaucon uses themythical story of “The Ring of Gyges” to prove that humansare inherently selfish. In this and many other situations, stories ofvarious kinds (accounts of some historical event, biographies, fables,parables, morality plays, etc) are designed to provide support forsome conclusion. It has often been said that a novel or some other workof fiction is an argument for socialism, freedom of expression, orsome other value.

One can understand the argumentative use of narratives in a variety ofways: as rhetorical embellishment, as a form of argument by analogy,as implicit generalization (the characters in a story functioning asvariables within such generalizations), or reasoning that requires thedevelopment of unique standards of argument assessment. According toFisher 1987, argument itself is best understood as narrative.According to Nussbaum 1990, literature is a way to better understand,and argue about, complex moral situations. Within informal logic,Walton, Reed, and Macagno 2008 identify narrative-based schemes ofargument while others continue to debate the role that narratives playin ordinary argument (see Govier and Ayer 2013, Olmos 2014, Plumer2015).

Informal logic’s interest in real life argument has, from thestart, been tied to its interest in theteaching of reasoningskills. In view of this, its interests overlap with fields anddisciplines that study education and pedagogy — links manifestin its own influence on critical thinking and the philosophy ofeducation (and movements like “Philosophy for Children”).

Some of the educational issues raised by informal logic are manifestin the development of critical thinking tests which attempt to measureargumentation skills. They are used to test the abilities of studentsor others and, in a self-reflective way, as an empirical way to testthe success of attempts to teach informal reasoning.

Critical thinking (or, even more so, creative thinking) skills are noteasily assessed using standardized tests which are designed for largescale use, and typically rely on multiple choice question and answers(see Sobocan 2021). In real life contexts, what counts as good arguing(and thinking) is open ended and unpredictable, dialectical, andinfluenced by pragmatic and contextual considerations which aredifficult to incorporate within standard tests. The CaliforniaCritical Thinking Test reflects the view of critical thinkingelaborated in “The Delphi Report,” commissioned by theAmerican Philosophical Association in 1987, a report that focuses on anarrow range of critical thinking skills which tends to oversimplifythe competencies required for good informal argument.

Ennis 2013 provides a comprehensive proposal for dealing with theissues raised by critical thinking tests, and with other challengesraised by attempts to teach critical thinking.

6. Informal Logic and Philosophy

The field of informal logic is a recent invention, but one thatcontinues historical attempts to understand and teach others how toargue. In the Western philosophical tradition, it begins with thesophists’ fifth century boast that they could teach others howto be successful arguers. In Aristotle it is manifest in hissystematic account of reasoning, which is expressly designed to teachothers how to argue well. Within the history of philosophy, one findsnumerous other attempts to formulate accounts of argument that can beused to explain, evaluate, and teach real life reasoning.

The practice of philosophy itself assumes (and frequently develops) anaccount of argument as it assembles evidence for differentphilosophical perspectives. Systems of informal logic assume, andoften depend upon, the resulting views of reason, rationality and whatcounts as evidence and knowledge. The philosophical issues in play aretied to complex, unsettled epistemological questions about evidenceand knowledge.

Mercier and Sperber (2011) argue that reasoning is a practice whichhas evolved from, and needs to be understood in terms of, the socialpractice of argumentation. Johnson 2000 pushes in the oppositedirection, arguing that a comprehensive account of argument must bebuilt upon a philosophical account of rationality. Goldman 1999situates knowledge in the social interactions that take place withininterpersonal exchange and knowledge institutions, emphasizinginformal argument and the constraints which make it a valuablepractice. A 2002 volume ofPhilosophica on HilaryPutnam’s philosophy suggests pragmatism as an epistemology thatbest fits informal logic as a discipline.

Some aspects of informal logic raise deep questions that haveimplications for logic and philosophy. One notable feature of informallogic as it is now practiced is a proliferation of different systemsof informal logic which approach the analysis and evaluation ofinformal reasoning in different ways — employing fallacies,AV criteria, argumentation schemes, methods of formal analysis,and other models of good argument. One implication is a broadening ofthe conditions for argument felicity.

Other issues are raised by informal logic’s recognition thatreal life arguments frequently employ visual images, non-verbalsounds, and other non-verbal elements, challenging the traditionalassumption that arguments are sets of sentences -- or the propositions(“the bearers of truth value”) that sentences refer to.However one understands visual and multimodal arguments, there is noeasy way to reduce them to sets of sentences, for there is no preciseway to translate what we see, hear, experience, etc. into words.

In its current state of development, informal logic’s connectionto philosophy does not lie in its influence on key philosophicaldisciplines so much as their influence on it. In North America andelsewhere, informal logic is a field in which philosophers applytheories of argument (rationality, knowledge, etc.) to everydayargument. In keeping with this, philosophers continue to be the corecontributors to informal logic; philosophy departments in colleges anduniversities continue to be the core departments that teach thecourses that are its pedagogical focus.

The influence of informal logic courses on the enormous numbers ofstudents that enrol in them require that we at least qualifyRescher’s remark (2005, p. 22) that: “The fact is thatphilosophy has little or no place in American popular (as opposed toacademic) culture... philosophy nowadays makes virtually no impact onthe wider culture of North America.” The extent to whichinformal logic’s attempt to broadly instill good reasoninghabits within public education and public discussion and debate isdifficult to judge.

Though informal logic addresses many issues relevant to corephilosophical disciplines (most notably, epistemology and philosophyof mind; evident in the work of Goldman, Crosswhite, Thagard, andothers), it has had limited impact on mainstream approaches to theirsubject matter. Woods 2000 has speculated on the reasons why. In part,informal logic’s position within philosophy reflects the broaderfragmentation of philosophy within North America, Rescher 2005 (p. 4)writing that: “The most striking aspect of contemporary Americanphilosophy is its fragmentation. The scale and complexity of theenterprise is such that if one seeks in contemporary Americanphilosophy for a consensus on the problem agenda, let alone foragreement on the substantive issues, then one is predestined to lookin vain.”

In this context, it can best be said that informal logic, like appliedethics, has become a standard offering that helps sustain philosophydepartments in North America by contributing to what Rescher describesas “The rapid growth of ‘applied philosophy’...[that] is a striking structural feature of contemporary NorthAmerican philosophy.” (p. 9). The goal of applied philosophy isphilosophically informed and nuanced reasoning that addresses complexreal life situations. Informal logic is one field which has made avaluable contribution to this goal.

Bibliography

• Ajdukiewicz, K., 1974.Pragmatic Logic, O. Wojtasiewicz(trans.), Dordrecht/Boston/Warsaw: D. Reidel Publishing Company &PWN – Polish Scientific Publishers. (English translation ofLogika pragmatyczna, originally published 1965.)
• Arnauld, Antoine, and Pierre Nicole, 1662.Logic, or, The Artof Thinking, Thomas Spencer Baynes (trans.), Edinburgh:Sutherland and Knox, 1850. [Arnauld and Nicole 1662 [1850] available online]
• Barwise, Jon and John Etchemendy, 1998. “Computers,Visualization, and the Nature of Reasoning,” in T. W. Bynum andJames H. Moor (eds.),The Digital Phoenix: How Computers areChanging Philosophy, pp. 93–116, London: Blackwell.
• Battersby, Mark and Sharon Bailin, 2011.“Fallacy identification in a dialectical approach to teaching critical thinking”,OSSA Conference Archive, Windsor: University of Windsor.
• Battersby, Mark, 2016.Is That a Fact? A Field Guide forEvaluating Statistical and Scientific Information, Peterborough:Broadview Press.
• Bennett, Bo, 2018.Logically … Fallacious: The UltimateCollection of over 300 Logical Fallacies, Sudbury, MA: ArchieBoyLLC.
• Bermejo Luque, Lilian, 2011.Giving Reasons: ALinguistic-Pragmatic Approach to Argumentation Theory, Dordrecht:Springer.
• Blair, J. Anthony (ed.), 2021.Studies in Critical Thinking Windsor: Windsor Studies in Argumentation (Volume 8).
• ––– and Christopher W. Tindale (eds.), 2020.Rigour and Reason: Essays in Honour of Hans Vilhelm Hansen Windsor: Windsor Studies in Argumentation (Volume 10).
• –––, 2015. “What Is Informal Logic?”Reflections on Theoretical Issues in Argumentation(Argumentation Library, Volume 28), Frans H. van Eemeren and BartGarssen (eds.), Dordrecht: Springer.
• –––, 2012.Groundwork in the Theory ofArgumentation: Selected Papers of J. Anthony Blair, Dordrecht:Springer.
• –––, 1996. “The Possibility and Actualityof Visual Arguments,”Argumentation and Advocacy,33(1): 23–39.
• Blair, J. Anthony and Ralph H. Johnson, 1980.Informal logic:the first international symposium, Inverness, CA :Edgepress.
• Bowell, Tracy and Gary Kemp, 2014.Critical Thinking: AConcise Guide, 4th ed., Routledge: London.
• Brinton, Alan and Douglas Walton, 1997.Historical Foundationsof Informal Logic, Aldershot: Ashgate Publishing.
• Budzynska, Katarzyna, Michal Araszkiewicz, BarbaraBogołȩbska, Piotr Cap, Tadeusz Ciecierski,KamilaDebowska-Kozlowska, Barbara Dunin-Kȩplicz, MarcinDziubiński, Michał Federowicz, Anna Gomolińska, AndrzejGrabowski, Teresa Hołówka, Łukasz Jochemczyk,Magdalena Kacprzak,Paweł Kawalec, Maciej Kielar, AndrzejKisielewicz, Marcin Koszowy, Robert Kublikowski, Piotr Kulicki, AnnaKuzio, Piotr Lewiński, Jakub Z. Lichański, Jacek Malinowski,Witold Marciszewski, Edward Nieznański, Janina Pietrzak, JerzyPogonowski, Tomasz A. Puczyłowski, Jolanta Rytel, Anna Sawicka,Marcin Selinger, Andrzej Skowron, Joanna Skulska, Marek Smolak,Małgorzata Sokół, Agnieszka Sowińska, PiotrStalmaszczyk, Tomasz Stawecki, Jarosław Stepaniuk, AlinaStrachocka, Wojciech Suchoń, Krzysztof Szymanek, Justyna Tomczyk,Robert Trypuz, Kazimierz Trzȩsicki, Mariusz Urbański, EwaWasilewska-Kamińska, Krzysztof A. Wieczorek, Maciej Witek,Urszula Wybraniec-Skardowska, · Olena Yaskorska, MariaZałȩska, Konrad Zdanowski, Tomasz Żurek, 2014.“The Polish School of Argumentation: A Manifesto,”Argumentation, 28(3): 267–282. .
• Browne, M. Neil and Stuart M. Keeley, 2018.Asking the RightQuestions: A Guide to Critical Thinking, 12th ed., EnglewoodCliffs: Prentice Hall.
• Burke, Michael B., 1994. “Denying the Antecedent: A CommonFallacy?”Informal Logic, 16(1): 23–30.
• Carney, James D. and Richard K. Scheer, 1964.Fundamentals ofLogic, New York: Macmillan.
• Copi, Irving, 1953.Introduction to Logic, New York:Macmillan.
• Crosswhite, James, 1996.The Rhetoric of Reason: Writing andthe Attractions of Argument, Madison: University of WisconsinPress.
• –––, 2013.Deep Rhetoric: Philosophy,Reason, Violence, Justice, Wisdom, Chicago: University of ChicagoPress.
• Dove, Ian, 2016. “Visual Scheming: Assessing VisualArguments,”Argumentation and Advocacy (Special Issue:Twenty Years of Visual Argument), D. Godden, Catherine H. Palczewski,and Leo Groarke (eds.), 52(4): 254–264.
• Dumke, G., 1980.Chancellor’s Executive Order 338,Chancellor’s Office, Long Beach: California StateUniversity.
• Eckstein, Justin 2018. “Figuring Sound”Informal Logic, 38(3): 341–345.
• Eemeren, Frans H. van, B. Garssen, E.C.W. Krabbe, F.A. SnoeckHenkemans, B. Verheij, and J.H.M. Wagemans, 2014,Handbook ofArgumentation Theory, Dordrecht: Springer.
• Eemeren, Frans H. van (ed.), 2002.Advances InPragma-Dialectics, Amsterdam: SicSat.
• Eemeren, Frans H. van and Rob Grootendorst, 1992.Argumentation, Communication, and Fallacies: A Pragma-DialecticalPerspective, Hillsdale, NJ: Lawrence Erlbaum Associates.
• Ennis, R.H., 2013. “Critical Thinking Across theCurriculum.” D. Mohammed & M. Lewiński (eds.),Virtues of Argumentation: Proceedings of the 10th InternationalConference of the Ontario Society for the Study of Argumentation(OSSA), Windsor, ON: OSSA, pp. 1–16,available online.
• –––, 2011. “Critical Thinking: Reflectionand Perspective” (Part I),Inquiry, 26(1):4–18.
• Feldman, Richard, 2009. “Thinking, Reasoning, andEducation,” in Harvey Siegel (ed.),Oxford Handbook ofPhilosophy of Education, pp. 67–82, Oxford: OxfordUniversity Press.
• Feteris, Eveline, Bart Garssen and Francisca Snoeck Henkemans,2011.Keeping in Touch with Pragma-Dialectics, Amsterdam:John Benjamins.
• Finocchiaro, Maurice A., 1997.“The Port-Royal Logic’s Theory of Argument,”Argumentation, 11: 393–410.
• Fisher, Walter R. 1987.Human Communication as Narration.Toward a Philosophy of Reason, Value, and Action, Columbia:University of South Carolina Press.
• Fogelin, Robert J. 1978.Understanding Arguments: AnIntroduction to Informal Logic, New York: Harcourt, Brace,Jovanovich.
• Gilbert, Michael, 2014.Arguing with people,Peterborough: Broadview Press.
• –––, 2001.How to Win an Argument, NewYork: MJF Books.
• –––, 1997.Coalescent Argumentation,Mahwah, NJ: Lawrence Erlbaum Associates.
• Godden, David, Catherine H. Palczewski, Leo Groarke (eds.), 2016.Twenty Years of Visual Argument: Special Issue,Argumentation andAdvocacy, Vol. 52, No. 4, Spring.
• Godden, David M., 2014. “Mill’s System of Logic”inThe Oxford Handbook of British Philosophy in the NineteenthCentury, W.J. Mander (ed.), Oxford: Oxford University Press, pp.44–70.
• –––, 2005. “Deductivism as an InterpretiveStrategy: A Reply to Groarke’s Recent Defense of ReconstructiveDeductivism,”Argumentation and Advocacy, 41(3):168–83.
• Goldman, Alvin I., 1999.Knowledge in a Social World,Oxford: Clarendon Press.
• Goodwin, Jean and Viviana Cortes, 2010. “Theorists’and practitioners’ spatial metaphors for argumentation: Acorpus-based approach,”Verbum, 23: 163–78.
• Govier, Trudy, 2019.A Practical Study of Argument,Enhanced 7th ed., Boston: Wadsworth.
• –––, 1999.The Philosophy of Argument,Newport News: Vale Press.
• –––, 1987.Problems in Argument Analysis and Evaluation, Amsterdam: Mouton de Gruyter/Foris (reprinted as Volume 6 in WindsorStudies in Argumentation).
• Govier, T. & L. Ayers, 2012. “Logic, Parables, andArgument,”Informal Logic, 32(2): 161–189.
• Grennan, Wayne, 1997.Informal Logic: Issues and Techniques: Aproposal for a new system of argument evaluation, Montreal:McGill-Queen’s University Press.
• Groarke, Leo A., Christopher W. Tindale, and Linda Carozza, 2021.Good Reasoning Matters!, 6th edition, Toronto: OxfordUniversity Press.
• Groarke, Leo, 2020. “How to Define an Informal Logic,”in Blair and Tindale (eds.),Rigour and Reason, pp.231–251.
• –––, 2019. “Matching Schemes of Argument:Verbal, Visual, Multimodal,” in Bart Garssen, David Godden,Gordon R. Mitchell, Jean H.M. Wagemans (eds.),Proceedings of theNinth Conference of the International Society for the Study ofArgumentation, Amsterdam: Sic Sat, pp. 443–457.
• –––, 2018. “Auditory Arguments: The Logic of ‘Sound’ Arguments”,Informal Logic, 38:3, 312–340.
• –––, 2015. “Going Multimodal: What is a Mode of Arguing and Why Does it Matter?”,Argumentation, 29(2): 133–155.
• –––, 1999. “Deductivism WithinPragma-Dialectics,”Argumentation, 13: 1–16.
• Hamblin, Charles Leonard, 1970.Fallacies, London:Methuen.
• Hansen, Hans V., 2012. “Are there methods of informal logic?” in F. Zenker (ed.),Argumentation: Community and Cognition,Proceedings of the 9th Conference of the Ontario Society for the Studyof Argumentation, pp. 1–13, Windsor: Centre for Research onReasoning, Argumentation, and Rhetoric.
• –––, 2002. “The Straw Thing of FallacyTheory: The Standard Definition of ‘Fallacy’,”Argumentation, 16(2): 133–155.
• Hansen, Hans V. and Robert C. Pinto (eds.), 1995.Fallacies:Classical and Contemporary Readings, University Park, PA:Pennsylvania State University Press.
• Harman, Gilbert H., 1965. “The Inference to the BestExplanation,”The Philosophical Review, 74(1):88–95.
• Harrison, Frank R. III, 1969.Deductive Logic and DescriptiveLanguage, London: Prentice Hall.
• Hitchcock, David, 2007. “Informal logic and the concept ofargument,” in Dale Jacquette (ed.),Philosophy of Logic(Volume 5, Handbook of the Philosophy of Science), Amsterdam:Elsevier, pp. 101–129.
• –––, 2002. “The Practice of ArgumentativeDiscussion,”Argumentation, 16(3): 287–298.
• –––, 1995. “Do Fallacies Have a Place inthe Teaching of Reasoning Skills or Critical Thinking?” in HansV. Hansen and Robert C. Pinto (eds.),Fallacies: Classical andContemporary Readings, pp. 319–327, University Park, PA:Pennsylvania State University Press.
• Hoffman, Michael H.G., 2016. “Reflective Argumentation: ACognitive Function of Arguing,”Argumentation, 30:1–33.
• Hughes, William, Jonathan Lavery and Katheryn Doran, 2014.Critical Thinking: An Introduction to the Basic Skills, 7thed., Peterborough: Broadview.
• Johnson, Ralph H., 2011. “Informal Logic andDeductivism,”Studies in Logic, 4(1): 17–37.
• –––, 2007. “Making Sense of‘Informal Logic’,”Informal Logic, 26(3):231–58.
• –––, 2000.Manifest Rationality: A PragmaticTheory of Argument, Mahwah, NJ: Lawrence Erlbaum Associates.
• –––, 1996 [2014].The Rise of InformalLogic, Newport News, VA: Vale Press (1996);Digital edition, University of Windsor: Windsor Studies in Argumentation (Volume 2,2014).
• Johnson, Ralph H. and J. Anthony Blair, 1997. “InformalLogic in the Twentieth Century,” in Douglas Walton and AlanBrinton (eds.),Historical Foundations of Informal Logic, pp.158–177. Aldershot, England: Ashgate.
• –––, 1994. “Informal Logic: Past andPresent,” in Ralph H. Johnson and J. Anthony Blair (eds.),New Essays in Informal Logic, pp. 1–19, Windsor:Informal Logic Enterprizes.
• –––, 1985. “Informal Logic: The Past FiveYears 1978–1983,”American PhilosophicalQuarterly, 22(3): 181–196.
• –––, 1977 [1994].Logical Self-Defense,1st edition (1977), 3rd edition (1994), Toronto: McGrawHill-Ryerson.
• Jørgensen, Charlotte, Christian Kock and LoneRørbech, 1995. “Hostility in Public Debate,” inFrans H. van Eemeren, Rob Grootendorst, J. Anthony Blair and CharlesWillard (eds.),Special Fields and Case Studies (Proceedingsof the Third ISSA Conference on Argumentation, Vol. IV), pp.365–73, Amsterdam: International Centre for the Study ofArgumentation.
• –––, 1991. “Rhetoric That Shifts Votes: ALarge-Scale Exploratory Study of Persuasion in Issue-Oriented PublicDebates,”Political Communication, 15:283–299.
• Kahane, Howard, 1971 [1995].Logic and Contemporary Rhetoric:The Use of Reason in Everyday Life, 1st edition (1971), 7thedition (1995), Belmont: Wadsworth.
• Kahane, Howard and Nancy M. Cavender, 2002.Logic andContemporary Rhetoric: The Use of Reason in Everyday Life, 9thEdition, Belmont: Wadsworth.
• Kišiček, Gabrijela 2018. “ Can we Translate Sounds into Words?”Informal Logic, Vol. 38, No. 3(2018), pp.346–361.
• –––, 2014. “The role of paralinguisticfeatures in the analysis of multimodal argumentation,” inProceedings of the 8th international conference onargumentation, University of Amsterdam: International Society forthe Study of Argumentation (ISSA).
• Kjeldsen, Jens, 2015. “ The Study of Visual and Multimodal Argumentation,”Argumentation, 29(2): 115–132.
• Koszowy, Marcin. 2010. “Pragmatic Logic and the Study ofArgumentation,”Studies in Logic, Grammar and Rhetoric,22(35): 29–44.
• Lazere, Donald, 1987. “Critical Thinking in College EnglishStudies,”ERIC Digest (ED284275), Urbana, IL: ERICClearinghouse on Reading and Communication Skills.
• Little, J. Frederick, 1980.Critical Thinking and DecisionMaking: A Methodology of Analysis, Evaluation and Review,Toronto: Butterworths.
• Lunsford, Andrea, John J. Ruszkiewicz, and Keith Walters, 2012.Everything’s an Argument, 6th Edition, Boston:Bedford/St. Martin.
• Mans, Dieter and Gerhard Preyer (eds.), 1999.Reasoning andArgumentation, Special Issue,Protosociology, 13.
• Mill, John Stuart, 1882.A System of Logic, Rationinative andInductive, Being a Connected View of the Principles of Evidence, andthe Methods of Scientific Investigation, 8th edition, New York:Harper & Brothers.
• Mercier, Hugo and Dan Sperber, 2011. “Why do humans reason?Arguments for an argumentative theory,”Behavioral and BrainSciences, 34: 57–111.
• Mochales, Raquel and Aagje Ieven, 2009. “Creating anArgumentation Corpus: Do Theories Apply to Real Arguments? A CaseStudy on the Legal Argumentation,”Proceedings of the 12thInternational Conference on Artificial Intelligence and Law, NewYork: Association for Computing Machinery.
• Munson, Ronald, 1976.The Way of Words: An InformalLogic, Boston: Houghton Mifflin.
• Nussbaum, Martha C., 1990.Love’s Knowledge: Essays onPhilosophy and Literature, Oxford: Oxford University Press.
• Olmos, Paula, 2014. “Classical Fables as Arguments:Narration and Analogy,” in Henrique Jales Ribeiro (ed.),Systematic Approaches to Argument by Analogy (ArgumentationLibrary, Volume 25), pp. 189–208, Dordrecht: Springer.
• Plumer, Gilbert, 2015. “On Novels as Arguments,”Informal Logic, 35: 488–507.
• Paul, Richard and Linda Elder, 2012.Fallacies: The Art ofMental Trickery, Tomales, CA: Foundation for CriticalThinking.
• Pinto, Robert C., 2001.Argument, Inference and Dialectic:Collected Papers on Informal Logic, Dordrecht: Kluwer.
• Pospesel, Howard, 2002.Introduction to Logic: PredicateLogic, 2nd edition, Saddle River: Pearson Education.
• Pospesel, Howard and David Marans, 1978.Arguments: DeductiveLogic Exercises, Saddle River: Pearson Education.
• Prakken, H. 2010a. “An abstract framework for argumentationwith structured arguments,”Argument and Computation,1: 93–124.
• –––, 2010b. “On the nature of argumentschemes,” in C.A. Reed & C. Tindale (eds.)Dialectics,Dialogue and Argumentation. An Examination of Douglas Walton’sTheories of Reasoning and Argument, pp. pp 167–185. London:College Publications.
• Puppo, Federico (ed.), 2019.Informal Logic: A ‘Canadian’ Approach to Argument, Windsor: Windsor Studies in Argumentation, Vol. 9.
• Rahwana, Iyad, Fouad Zablitha, and Chris Reed, 2007. “Layingthe foundations for a World Wide Argument Web,”ArtificialIntelligence, 171 (July-October): 897–921.
• Reed, C.A. and T.J. Norman, 2004.Argumentation Machines: NewFrontiers in Argument and Computation, Dordrecht: Kluwer AcademicPublishers.
• Reed, C.A. and D.N. Walton, 2002. “Applications of Argumentation Schemes” in Hansen, H.V., C. W. Tindale, J.A. Blair, and R.H. Johnson (eds.),Argumentation and Its Applications: Proceedings of the 4thConference of the Ontario Society for the Study of Argument, pp.1–12, Windsor: Ontario Society for the Study ofArgumentation.
• Rescher, Nicholas, 2005.Studies in Twentieth CenturyPhilosophy, Frankfurt: Ontos.
• Rodes, Robert E. and Howard Pospesel, 1991.Premises andConclusions: Symbolic Logic for Legal Analysis, Notre Dame:University of Notre Dame Press.
• Ryle, Gilbert, 1954.Dilemmas: The Tarner Lectures,Cambridge: Cambridge University Press.
• Seay, Gary and Susana Nuccetelli, 2012.How to ThinkLogically, 2nd. ed., Boston: Pearson.
• Siegel, Harvey, 1988.Educating reason: rationality, criticalthinking, and education, New York: Routledge.
• Shelley, Cameron, 2003. “Aspects of visual argument: A studyof the ‘March of Progress’,”InformalLogic, 21(2): 92–112.
• Sobocan, Jan (ed.), 2021.Critical Thinking, Education andAssessment: Can Critical Thinking Be Tested?, 2nd ed. Windsor:Windsor Studies in Argument.
• Thagard, Paul, 2011. “Critical Thinking and Informal Logic: Neuropsychological Perspectives,”Informal Logic, 31(3): 152–70.
• Tindale, Christopher W., 2021.The Anthropology of Argument:Cultural Foundations of Rhetoric and Reason, New York:Routledge.
• –––, 2010.Reason’s Dark Champions:Constructive Strategies of Sophistic Argument, Columbia: SouthCarolina Press.
• –––, 2004.Rhetorical Argumentation:Principles of Theory and Practice, Ithaca, NY: SagePublications.
• –––, 1999.Acts of Arguing: A RhetoricalModel of Argument, Albany, NY: State University of New YorkPress.
• Toulmin, Stephen, 1958 [2003].The Uses of Argument,Cambridge: Cambridge University Press; revised edition, 2003.
• Tseronis, Assimakis and Charles Forceville, eds. 2017.Multimodal Argumentation and Rhetoric in Media Genres,(Argumentation in Context, Volume 14), Amsterdam: John Benjamins.
• Verheij, Bart, 2014. “Argumentation and ArtificialIntelligence,” Chapter 11 in Eemeren et al., 2014.
• –––, 1999. “Automated Argument Assistancefor Lawyers,”Proceedings of the Seventh InternationalConference on Artificial Intelligence and Law, New York:Association of Computing Machinery, pp. 43–52.
• Walton, Douglas N., 2012. “Story similarity in argumentsfrom analogy,”Informal Logic, 32: 190–221.
• –––, 2007.Dialog Theory for CriticalArgumentation, Amsterdam: John Benjamins Publishing Company.
• –––, 2004.Abductive Reasoning,Tuscaloosa, University of Alabama Press.
• –––, 2000.Scare Tactics: Arguments thatAppeal to Fear and Threats (Argumentation Library: Volume 3),Berlin: Springer.
• –––, 1989.Informal Logic: A Handbook forCritical Argumentation, New York: Cambridge UniversityPress.
• Walton, Douglas, Christopher Reed, Fabrizio Macagno, 2008.Argumentation Schemes, Cambridge: Cambridge UniversityPress.
• Weston, Anthony, 2018.A Rulebook for Arguments, 5th ed.,Indianapolis: Hackett.
• Whately, Richard, 1826.Elements of logic, London: B. Fellowes.
• –––, 1830.Elements of rhetoric, 3rdedition, Oxford: W. Baxter.
• Wigmore, John Henry, 1913.The principles of judicial proof:as given by logic, psychology, and general experience, and illustratedin judicial trials, Boston: Little Brown.
• Wilson, David Carl, 2020.A Guide to Good Reasoning:Cultivating Intellectual Virtues, 2nd edition, Twin Cities:University of Minesota Libraries.
• Woods, John and Douglas Walton 1982.Argument: The Logic ofthe Fallacies, Roronto: McGraw-Hill Ryerson.
• Woods, John, 2000. “How Philosophical is Informal Logic?”Informal Logic, 20(2): 139–167.
• –––, 1995. “Appeal to Force,” inHansen and Pinto 1995, pp. 240–250.
• Zenker, F. 2013.Bayesian Argumentation: The practical side ofprobability (Synthese Library 362), Dordrecht: Springer.

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Other Internet Resources

• ARGDIAP: A Polish initiative dedicated to the issues of argumentation, dialogue and persuasion
• ARG-tech: Centre for Argument Technology
• Argument and Computation
• Centre for Argument Technology
• The listserv ARGTHRY: Argument Theory
• The Arguer’s Lexicon, A lexicon of the names of informal logicians and other argumentation theorists.
• Argumentation et Analyse du Discours
• Automated Argument Assistance
• Association for Informal Logic and Critical Thinking: AILACT
• Centre for Research in Reasoning, Argumentation & Rhetoric
• Cogency: Journal of Reasoning and Argumentation
• COMMA: Computational Models of Argument
• Fallacies, entry by Bradley Dowden in theInternet Encyclopedia ofPhilosophy, J. Fieser (ed.)
• Fallacies: The Nizkor Project
• Foundation for Critical Thinking
• Informal Logic
• Ontario Society for the Study of Argumentation (OSSA)
• The Periodic Table of Arguments
• Silva Rhetoricae: The Forest of Rhetoric
• Studies in Logic, Grammar and Rhetoric
• Virtues and Arguments: A Bibliography
• Windsor Studies in Argumentation

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Acknowledgments

The author would like to acknowledge and thank the members of ARGTHRY,Tony Blair, and the SEP reviewer for many corrections andsuggestions.