Stanford University

Informal Logic (Stanford Encyclopedia of Philosophy)

The pedagogical and practical interests that characterize informal
logic are already evident in ancient times. The First Sophistic is a
movement motivated by the notion that one can teach the art of
logos in a way that can be useful in public discussion and
debate. Aristotle’s rhetorical and logical works are especially
notable for their systematic attempts to understand and teach the
principles of real life arguing. Within informal logic and
argumentation theory, his views and general outlook remain relevant

Significant attempts to develop a systematic approach to informal
arguments emerge in early modern times. The Port Royal Logic
(Arnauld & Nicole 1662), initially titled Logic or the Art of
, was first published in French in 1662. It quickly
established itself as an often celebrated and sometimes disdained
introduction to the art of argument. Since its first publication, it
has enjoyed more than fifty French editions and five popular English
translations. Describing logic as “the art of directing reason
aright, in obtaining the knowledge of things, for the instruction both
of ourselves and others” (25), it provides a practical account
of good and poor argument. Its account of logical methods discusses
fallacies, syllogisms, definitions, deductive and probable reasoning,
among other topics, emphasizing the discussion of real rather than
concocted examples of arguing (see Finocchiaro 1997).

One finds other analogues of today’s approaches to informal reasoning
in nineteenth century textbooks which aim to improve everyday
reasoning via public education that emphasizes logical and rhetorical
concerns. Richard Whatley is of special note in this regard. He began
his career as a professor of political economy at Oxford and was then
appointed Archbishop of Dublin for the Church of Ireland. During his
time in office, he attempted to establish a national and non-sectarian
system of education, writing texts on reasoning that could serve this
purpose. In many ways, his Elements of Logic and Elements
of Rhetoric
(Whately 1826, 1830) are rough analogues of
contemporary textbooks of informal logic and argumentation theory.

The trends that give rise to informal logic as a unique discipline of
study coalesce in North America in the late 1960s. This was a time
when social upheaval and protests against the War in Vietnam
popularized calls for an education that was relevant to the issues of
the day. In universities and colleges, this stimulated an interest in
the logic of everyday argument. One question this raised was the
extent to which informal arguments could be studied and analyzed using
the methods of formal logic: propositional logic, truth tables,
syllogisms, and the predicate calculus. Many of those teaching
everyday arguments criticized treatments like the ones found in Irving
Copi’s popular (1953) Introduction to Logic (see Johnson 1996
and Blair 2015).

In Logic and Contemporary Rhetoric: The Use of Reason in Everyday
, Kahane 1971 embraced real life argument in a broad way,
including a wide range of examples of real life arguing taken from
newspapers, the mass media, advertisements, books and political
campaigns. In comparison with Copi’s many concocted examples, other
authors did a better job melding classical formal logic with everyday
arguments. Harrison 1969 is a notable example. Pospesel published a
number of texts which illustrate how the patterns of inference that
characterize propositional and syllogistic logic appear in real life
contexts (see Pospesel and Marans 1978, Rodes and Pospesel 1991, and
Pospesel 2002). Little 1980 developed a critical thinking methodology
for everyday argument analysis and decision making which included
propositional and syllogistic reasoning as critical components.

In part because they wanted a much broader account of naturally
occurring argument that they found in classical logic, Toulmin’s
The Uses of Argument (1958) and Hamblin’s Fallacies
(1970) moved in new directions, developing alternative accounts of
argument. Hamblin attempted to reinvigorate fallacies as an approach
to understanding ordinary argument. In the development of informal
logic, their views have become theoretical touchstones for many
seeking to develop an informal logic.

One important catalyst for a systematic approach to informal argument
was the Critical Thinking Movement (described in Siegel 1988, Ennis
2011). It argued that the critical scrutiny of our beliefs and
assumptions should be a fundamental goal of education. What this means
has been variously interpreted (sometimes in ways that imply problem
solving, so called “lateral thinking”, and/or information
literacy), but a recurring theme is the importance of understanding
argument and argument assessment. In 1980, a California State
University Executive Order required post secondary institutions in the
state include formal instruction in critical thinking in their
curriculum. According to the order: “Instruction in critical
thinking is to be designed to achieve an understanding of the
relationship of language to logic, which should lead to the ability to
analyze, criticize, and advocate ideas, to reason inductively and
deductively and to reach factual or judgmental conclusions based on
sound inferences drawn from unambiguous statements of knowledge or
belief” (Dumke 1980, Executive Order 338).

The idea that the analysis of ordinary arguing could best be furthered
by creating an “informal logic” originated in the work of
Johnson and Blair at the University of Windsor. Their textbook,
Logical Self-Defense (1977), was an attempt to provide a
systematic approach to the study and teaching of informal argument.
The Informal Logic Newsletter they conceived and edited (now
the journal Informal Logic) successfully established informal
logic as a field for discussion, development and research. Forty years
later, the result is an established body of literature and a standard
(but evolving) set of topics, problems, and issues.

Other journals that have played a role in the rise of informal logic
include Argumentation, Philosophy and Rhetoric,
Argumentation and Advocacy (formerly the Journal of the
American Forensic Association
), Teaching Philosophy,
Inquiry: Critical Thinking Across the Disciplines and, more
recently, Cogency and Argument and Computation. The
journals ProtoSociology (1999) and Studies in Logic,
Grammar, and Rhetoric
(2009) have published special issues
devoted to topics in informal logic.

Since its inception, the development of informal logic has been
intertwined with pedagogical attempts to improve the ways in which
students are taught to reason well. These attempts have given rise to
hundreds (possibly thousands) of textbooks used to teach argumentation
skills to university and college students in Canada, the United
States, the United Kingdom, and a growing number of other countries.
The available texts take many different approaches to the subject and
offer many theoretical as well as pedagogical innovations. Currently
popular texts include Govier 2014 (7th ed.); Groarke & Tindale
2013 (5th ed.); Bowell and Kemp, 2010 (3rd ed.); Browne & Keeley
2010 (10th ed.); Fisher 2011 (2nd ed.); Seay & Nuccetelli 2012
(2nd ed.); Battersby 2016 (2nd ed.); Weston 2009 (4th edition); and
Hughes, Lavery & Doran 2014 (7th ed.).

Outside of the English speaking world, the goals of informal logic
have been pursued in the Polish tradition of “pragmatic
logic”, which promotes the tools of logic as a component of
general education which can ensure that students think more clearly
and consistently; express their thoughts and ideas systematically and
precisely; and justify their claims with proper inferences (see
Koszowy 2010 and Ajdukiewicz, K. 1974).

Increasingly, the development of informal logic incorporates
approaches to discourse and argumentation found in cognate disciplines
and fields like Formal Logic, Speech Communication, Rhetoric,
Linguistics, Artificial Intelligence, Semiotics, Cognitive Psychology,
and Computational Modelling. Considered from this perspective,
informal logic is one component of a much broader multi-disciplinary
attempt to develop an argumentation theory that can provide a
comprehensive account of real life reasoning.

In the course of their development, both informal logic and
argumentation theory have been nurtured and highlighted at a number of
international conferences. They include eleven Windsor conferences
hosted by the Ontario Society for the Study of Argumentation (OSSA);
seven Amsterdam conferences hosted at four-year intervals by the
International Society for the Study of Argumentation (ISSA); five
Tokyo Conferences on Argumentation hosted by the Japanese Debate
Association; seven COMMA conferences on computational models of
argument; four Chilean conferences on Argumentation, Psychology of
Reasoning and Critical Thinking; and a Polish series of
“ArgDiaP” workshops (dealing with argumentation, critical
thinking, dialogue and persuasion).

1.1 Formal and Informal Logic

The relationship between formal and informal logic is complex, and in
some ways controversial. As it is practiced today, informal logic is
an offshoot of classical logic which shares a premise and conclusion
conception of argument, many theoretical notions, and a similar
conception of the elements of good argument. The relationship is too
complex to be discussed in detail here, though some general comments
may help situate it and the controversies it sometimes gives rise to.

Historically, some key informal logicians have suggested it as a
theoretical alternative to formal logic. In his list of features that
characterize informal logic, Johnson 1996 [2014] (p. 11) lists
“dissatisfaction with formal logic as the vehicle for teaching skill
in argument evaluation and argument formation” and “A desire to
provide a complete theory of reasoning that goes beyond formal
deductive and inductive logic.”

One might take a different view. Informal logic is “informal” insofar
as it studies arguments as they occur in natural language discourse
rather than formal languages of the sort that characterize
propositional logic, the predicate calculus, modal logic, etc.
(languages which have rigorously specified syntax, semantics and
grammar, and clearly defined proof procedures). This is an important
point but it does not negate informal logic’s connections to formal
logic, especially as there is no consensus on the question how to best
pursue the study of such arguments and informal logicians sometimes
deploy formal methods of analysis (or mix formal and informal

Certainly there are aspects of everyday reasoning and argument which
can usefully be analyzed and studied using formal methods. Syllogistic
logic is one of the first formal approaches to argument and is,
historically and today, frequently used to analyze everyday
argumentation. Within informal logic, the general idea that logic
should focus on the logical form of an argument rather than its
specific content manifests itself in the common notion that informal
logic should assess ordinary arguments by treating them as instances
of different argument schemes (schemes that include standard deductive
forms of argument like modus ponens, modus tollens
and disjunctive syllogism).

The broader theoretical question posed by those who see formal and
informal logic as competing approaches to informal argument may be put
as the question: “Does Informal Logic deal with the issues of the
analysis and assessment of informal argument better than Formal Logic
by avoiding translation to artificial formal languages and the use of
mathematics?” This is a question which raises complex issues which lie
beyond the scope of the present article, but it may help to say that
the proper answer to it varies depending on at least three variables:
one’s purpose in studying informal argument; the kinds of informal
arguments one considers; and the kinds of formal systems in question.

The purpose of informal logic is a broadly disseminated understanding
of the difference between strong and weak argument which focuses on
teaching and on argument in public discourse and interpersonal
interactions. Formal methods can play a role in this regard,
especially in cases in which they provide a more precise account of
particular kinds of argument (e.g., deductive arguments, arguments in
dialogue, and probabilistic arguments). But even in these cases, the
ultimate aim of informal logic is ordinary language argument
characterized by careful language and the principles of good

There are many informal arguments which are difficult to translate
into formal languages like those that characterize classical logic,
but the possibility of formally studying and analyzing such arguments
grows as formal logic develops formal frameworks that include
defeasible (non-monotonic) logic and probability theory (which is
emerging as one theoretical approach to informal reasoning — see
Zenker 2013). Some of the issues that this raises are evident in
informal logic’s interaction with AI and computational modeling, which
depend for their development on ways in which ordinary language
arguing can be understood within formal systems. Some now common
aspects of informal logic’s approach to argument (for example,
argumentation schemes) have already influenced their attempts to
account for ordinary reasoning.

1.2 Informal Logic within Argumentation Theory

The broader interdisciplinary study of real life argument is often
called “argumentation theory.” Above and beyond the study
of arguments, it studies the broader contexts in which arguments are
embedded and the conditions (institutional, psychological,
educational, etc.) which give rise to disagreement, arguing and
argument. In addition to informal logic, argumentation theory
incorporates studies and insights from the fields of formal logic,
cognitive psychology, rhetoric, dialectics, computational modeling,
semiotics, communication studies, Artificial Intelligence and other
related disciplines. In the study of actual argument, these various
fields frequently intersect and influence one another.

Already in ancient times, the broader study of argument encompassed
logic, rhetoric, and dialectics. Each approached argument from a
particular point of view and gave rise to a distinct tradition within
argumentation theory. Rhetoric continues to see arguing as a vehicle
for persuasion; dialectic understands arguing as an exchange between
two or more arguers; and logic emphasizes the probative or epistemic
merit of an argument, making a good argument an argument which
justifies the point of view that it proposes.

Though it emphasizes the epistemic merit of an argument, informal
logic has evolved in a way that incorporates elements of rhetoric
and/or dialectics. The move in this direction has been motivated by
the same goal that motivates informal logic in the first place, i.e.
the desire to have an adequate theory of real life arguing. This
requires some account of the rhetorical and dialectical features of
argument, for they can be key components of an argument’s success.

In real life arguing, most arguments function as a response to
disagreement. Arguers aim to justify the standpoint they defend in a
way that convinces an intended audience or interlocutor. As rhetoric
emphasizes, the former is more readily accomplished when one
recognizes and responds to the beliefs and attitudes of the audience
one addresses. As dialectics holds, successful arguments consider (as
Johnson 2000 emphasizes) and respond to the likely objections to their
point of view. For this and other reasons, informal logic is a field
of argumentation theory which borrows from, and intersects with,
rhetoric, dialectics, and with many other argumentation disciplines
(Bermejo Luque 2011 proposes a theory of argument that usefully
illustrates the intersection of these various fields).

In view of its pedagogical goals, informal logic has additional ties
to educational movements which aim to make arguing and reasoning a
central component (or the very cornerstone) of education. This has
made informal logic a key element of the Critical Thinking
, which promotes models of education which emphasize
reasoning skills, critical self-reflection and the scrutiny of
students’ assumptions, beliefs and decisions.

One might compare North American approaches to informal logic to
pragmatic logic as it has been developed in the Polish
logical tradition (Koszowy 2010), where it is one component of the
Polish School of Argumentation. The latter brings together a multitude
of formal and informal approaches to argument. It has outlined its
research program in a Polish Manifesto (Budzynska et al. 2014). One
might easily describe informal logic as it has developed in North
America and pragmatic logic as it has developed in Poland as two
distinct (but in many ways, similar) attempts to create a satisfactory
informal logic.

Blair 2015 divides the work of informal logic in two, comprising the
interpretive task of recognizing arguments (and
“extracting” them from the discourse in which they are
embedded), and the evaluative task of assessing them. Both tasks
assume some account of what counts as argument.

In ordinary discourse, the word “argue” often means
“to disagree” (usually it carries the implication that
someone does so insistently or aggressively). In argumentation theory,
argument in the sense of disagreement is often called
“argument-2” (see Goodwin 2001). Like other logics,
informal logic focuses on arguing in a narrower sense, understanding
an argument as an attempt to provide evidence in favour of some point
of view. This can usefully be called an evidentiary account
of argument. It makes arguing an intentional act (a speech or
communication act) which is usually embedded in argument in the
broader sense, functioning as an attempt to resolve the disagreement
this implies.

Informal logic understands arguments in the evidentiary sense as
collections of premises and conclusions. The premises provide the
evidence that supports the conclusion. Hitchcock 2007 defines an
argument as “a claim-reason complex” consisting of (1) an
act of concluding, (2) one or more acts of premising (which assert
propositions in favour of the conclusion), and (3) a stated or
implicit inference word that indicates that the conclusion follows
from the premises. This makes arguments intentional acts that
incorporate (1), (2) and (3).

A simple example that illustrates what this means in practice is the
following excerpt from an opinion article in the Western
(25/10/08), which criticized conservative groups
unwilling to support any kind of embryonic research.

EXAMPLE 1: This [opposition to embryonic research] is shortsighted and
stubborn. The fact is, fetuses are being aborted whether conservatives
like it or not. Post-abortion, the embryos are literally being thrown
away when they could be used in lifesaving medical research. It has
become a matter of religious and personal beliefs, and misguided ones
at that. Lives could be saved and vastly improved if only scientists
were allowed to use embryos that are otherwise being tossed in the

We may analyze this argument as the following claim-reason

Premise: Fetuses are being aborted anyway.

Premise: Lives could be saved and vastly improved if
scientists were allowed to use embryos that are otherwise being tossed
in the garbage.

Inference Indicator: (implicit, unstated):

Conclusion: The conservative opposition to embryonic research
is shortsighted and stubborn.

The following two examples are simple arguments that illustrate some
of the issues that arise when we try to identify and extract arguments
from their naturally occurring contexts. Both are (slightly amended)
reports of arguments taken from a front page article in the New
Hampshire Rockingham News (30/8/2002) which discusses a court
case which sent the organizer of a series of dog fights to jail for
cruelty to animals.

EXAMPLE 2: The attorney for the defendant asserted that the sentence
handed down by Judge Abrahamson did not fit the crime because it was
unprecedented in length.

EXAMPLE 3: A co-ordinator for the Humane Society supported a prison
sentence, claiming that the minor penalties normally associated with
misdemeanour convictions are not a sufficient deterrent in this

In the first case (EXAMPLE 2) we can summarize the reported argument
as follows.

Premise: The sentence (handed down by Judge Abrahamson) was
unprecedented in length.

Inference Indicator: …because…

Conclusion: The sentence handed down did not fit the crime.

Here the word “because” functions as an inference
indicator, more precisely a premise indicator, which indicates
premises in support of a conclusion. One sign of argument in ordinary
discourse is an inference indicator (a word like “so,”
“hence,” “therefore,” “because,”
“thus,” etc.), but indicator words are used in other ways
as well. Words like “because” may, for example, signal an
explanation rather than an argument, a causal connection, emphasis of
some sort, a temporal order, and so on. In the process of recognizing
many arguments, this means that a theory of argument needs to
distinguish the different uses of indicator words.

In other cases (as in EXAMPLE 1 and EXAMPLE 3) arguments are
communicated without using inference indicators. In ordinary
discourse, a list of statements may be understood as a series of
claims or as an attempt to justify one of the statements with the
others. The statements “Small businesses are major contributors
to the economy. They account for over two-thirds of employment
opportunities.” (EXAMPLE 4) are from a Chamber of Commerce
statement on small business. They can be understood as two of a series
of claims that someone is making about small businesses or,
alternatively, as a conclusion followed by a premise that supports it.
In deciding when we have an instance of argument, we must usually rely
on context to determine which interpretation is correct.

Still other issues arise because important aspects of an argument may
be implicit or unclear in ordinary discourse. Statements may be
conveyed by (rhetorical) questions like: “Can anyone seriously
believe…?” “Are you joking?” “Could the
defendant have been in two places at once?” Often, the
components of an argument are interspersed with digressions and
repetitious remarks that are not relevant to it or its assessment. In
the process of extracting an argument from its context, this may mean
that we must recognize what is implicit but relevant to the argument
at the same time that we discard what is explicit but redundant or

In examples 2 and 3, arguments depend on implicit claims which need to
be considered when assessing the arguments. In the process of
identifying the components of an argument, such claims are standardly
identified as “implicit” premises (or conclusions). In our
two examples, this means that we can identify the components of the
arguments as:


Premise: The sentence (handed down by Judge Abrahamson) was
unprecedented in length.

Implicit Premise: Sentences for crimes should not be of
unprecedented length.

Inference Indicator: …because…

Conclusion: The sentence handed down did not fit the


Premise: The minor penalties normally associated with
misdemeanour convictions are not a sufficient deterrent in this case.

Implicit Premise: Penalties for crimes should have a
deterrent effect.

Inference Indicator: (implicit: (…therefore…)

Conclusion: The prison sentence is appropriate.

It is important to recognize implicit premises and conclusions because
they are elements of argument that need to be analyzed and assessed in
any attempt to evaluate the arguments that contain them. In EXAMPLE 3,
for example, the question whether punishments should be assigned by
considering their deterrent effects is a key issue that needs to be
considered in deciding whether the argument provides convincing
evidence for its conclusion. In cases in which implicit premises or
conclusions play a role in arguments, a comprehensive theory of
argument must tell us how to choose between the competing alternatives
that might be proposed (by, e.g., postulating implicit premises with a
broader or narrower scope).

2.1 A Broader Account of Argument

Hitchcock’s account of argument is purposely broad, in a way that
highlights an expansion of the notion of argument that has
characterized the evolution of informal logic. Originally, paradigm
examples of argument were taken to be arguments which attempt to
establish some conclusion as plausibly true. As does the following
argument for plate techtonics: “South America and Africa
probably began as a single continent, for the Eastern and Western
contours are remarkably symmetrical.” It can still be said that
arguments that provide evidence for the truth of their conclusions are
an important subset of real life arguments, but the study of actual
arguing has underscored the point that arguments are used in many
other ways.

Arguments are, for example, often used in situations of negotiation
(in collective bargaining, e.g.), in which the aim of arguers is not
truth so much as agreement (and the promotion of their own interests).
In other cases arguing may be an attempt to establish consensus, to
instill fear or hope or some other emotional state, or to incite
people to behave in a certain way (to take up arms against a foe, or
to support social change). Hoffman 2016 emphasizes the role that
argument plays in stimulating reflection and raising questions about
one’s own reasoning.

Hitchcock’s account of argument accommodates most of these uses,
subsuming the possibility that premises and conclusions may be speech
acts of different sorts. In particular, it allows a premise to be
forwarded by any communication act which asserts a proposition
(including, e.g., suggesting, hypothesizing, insulting and boasting);
and allows a conclusion to be a request for information (“You
were there, so what was it like?”); a request to do something
(“The children are shivering, so please close the door.”);
a commissive (“I know it matters to you, so I promise to go
tomorrow.”), an expressive (“What we did was inexcusable,
so we apologize.”) or a declarative (“The evidence shows
that you committed an assault, so I find you guilty as
charged.”). This broadening of the notion of argument is an
essential way to recognize and distinguish the diverse roles that
argument and inference actually play in real life contexts.

2.2 Visual Argument

In a different way, the conception of argument informal logic assumes
has been broadened even further as informal logicians expand its scope
to include the frequent instances of argument that utilize non-verbal
elements. Kjeldsen 2015 provides a comprehensive overview of the study
of visual arguments – arguments which employ non-verbal visuals
(which may include photographs, film, art, cartoons, graphs, diagrams,
and architecture). As Hitchcock notes, “a poster with a giant
photograph of a starving emaciated child and the words ‘make
poverty history’ can reasonably be construed as an
argument”. Drawings in a geometric proof, diagrams and
documentary film provide many other examples of visual argument. One
might compare the expansion of informal logic to account for such
arguments to the attempt to expand formal logic to allow visual
deductions (see Barwise and Etchemendy 1998).

Considered from the point of view of the evidentiary account of
argument, visual arguments are common, for visuals are often invoked
in order to provide evidence for some conclusion (that someone is
guilty of a crime, that a particular house is worth buying, or that a
work of art is a masterpiece). Consider the following two photographs,
taken by the NASA Mars rover Curiosity, which were heralded as the
first proof that the planet Mars has water.


nasa rover

The first photo shows the results of an initial dig by the rover, the
second provides a view of the same dig four Mars days (sols) later.
The sequence shows white areas of the surface receding or (in the
bottom left hand corner) entirely disappearing, an observation which
was taken to show that these surfaces are water in the form of ice
(ice which begins to evaporate when the dig exposes it to the sun).

Like most visual arguments, this example mixes visual and verbal cues
(i.e. visuals and verbal claims). We might identify the key components
of one elaboration of the argument (presented in a news exchange) as


(Visual) Premise: First photograph of the dig.

(Visual) Premise: Second photograph of the dig.

(Verbal) Premise: “The most plausible way to explain
the changes we see in the the photographs is by postulating the
evaporation of water ice.”

Inference Indicator: “We can conclude that…”

Conclusion: “…there is water on the planet

In a case like this, the arguing is inherently visual because our
looking at the photographs is an essential element of the
reasoning. It is this looking (combined with the attendant
explanation) which is supposed to convince us of the conclusion.

The use of visual images in arguments suggests that the traditional
assumption that arguments are sets of sentences — or the propositions
that sentences refer to — is too limiting. More deeply, it raises the
fundamental question whether arguments are best understood as
collections of propositions (the bearers of truth-value that
declarative sentences refer to). One way to maintain this account is
by understanding the images in visual arguments as another way to
forward propositions or sets of propositions. However one understands
visual arguments, there is no easy way to reduce them to sets of
sentences, for there is no exact way to translate what we see into
words (in part because it is difficult to choose between the many
different ways in which we can describe most visual images).

Like verbal arguments, visual arguments may take many different forms.
A further example is the advertisement below (EXAMPLE 5). In this
case, the title “Just Add Vodka” is superimposed over a
bottle of vodka spilling its contents onto a hamlet below. Outside the
splash of vodka, the time of day (dusk), the inactivity, and the
darkness suggest a sleepy hamlet where there is nothing to do at
night. This contrasts sharply with the bustling city scape that
springs life in the places where the vodka splashes to the ground
— a cityscape that boasts a nightlife with skyscrapers and
activity: lights, people, nightclubs, bars, and restaurants.


vodka print ad

If we try to understand this image as a literal depiction of reality,
it makes no sense: bottles of vodka are not so absurdly large, they do
not pour their contents on sleepy hamlets, and would not create
Manhattan streetscapes if they did. This tells us that the image is a
visual metaphor, another common way to use visuals in arguing. In this
case the metaphor is readily understood as one of transformation, the
vodka being featured as a liquid catalyst for change.

We might summarize the argument as follows.


Premise: Image [of the vodka transforming a sleepy life into
one of cosmopolitan excitement].

Inference Indicator (implicit): …therefore…

Conclusion: You should “Just Add Vodka” to your

One might add to this summary of the argument the implicit premise
that a life of cosmopolitan excitement is desirable, for this is a key
claim the argument assumes: and one that would need to be discussed in
an assessment of the argument. As with many visuals, one could analyze
the meaning of the image in much greater detail by discussing the
semiotic aspects of visuals (one might, for example, discuss the
image’s apparent sexual innuendo). Once one recognizes the
advertisement (and many other advertisements) as an attempt to provide
a reason for buying something, we can analyze and assessed it using
standard techniques developed by informal logic.

Informal logicians have extended their account of argument to include
visual arguments for the same reason they have tried to extend logical
methods to the analysis of ordinary argument: because their goal is an
account of the kinds of arguing that play an important role in real
life arguing. Visual arguments are especially important at a time in
which digital communication makes it so much easier to create and
transmit images. In the world of real life arguing, this is ushering
in an era in which arguments increasing employ photographs, videos,
political cartoons, 3D modeling and other visuals to prove matters in
courts, in social and political debate, in medical diagnosis, and so

2.3 Modes of Arguing

Studies of visual argument are increasingly tied to discussions of
“multimodal” arguing. Multimodality is a key notion in
social semiotics, which suggests that there are many different modes
of communication which can be used to make meaning. In argumentation
theory, multimodality has emerged as the idea that there are different
modes that can be employed in constructing arguments. Within informal
logic, Gilbert 1997 was the first to suggest that there are different
modes of arguing that need to be distinguished in a theoretical
analysis of argument (his modes are discussed below).

Maintaining informal logic’s standard focus on arguments in the
premise and conclusion sense, Groarke 2015 expands the realm of
argument to include, not only visuals, but tastes, smells, musical
notes and other non-verbal phenomenon. On this account, these
non-verbal entities may be key components of an argument (typically as
premises). An argument constructed using a particular mode employs
constituents in that mode (which may be words, non-verbal sounds,
visuals, tastes, and so on). On battlefields, for example, doctors
have traditionally diagnosed infections using a mode of arguing that
can be described as “argument by smell.” In such cases,
the scent they smell functions as evidence (as an olfactory premise)
for the conclusion that the infection is (or is not) anaerobic.

EXAMPLE 7 describes a different instance of multimodal argument which
employs arguing “by taste.”


A friend tries to convince you that “Frogs Leap PS 2015”
is an exceptional Petite Syrah by quoting high praise in a wine guide
and by handing you a glass with the comment “Taste it and you
will see.”

One strand of this argument is a standard appeal to authority (the
authority of the wine guide) which is composed of words. The other is
an argument by taste which uses taste to support the proposed
conclusion — that Frogs Leap PS 2015 is an exceptional Petite Syrah.
We can summarize this second strand of argument as:


Premise: Tasting of the wine

Inference Indicator: …Taste it and see…

Conclusion: Frogs Leap PS 2015 is an exceptional Petite

An approach to informal argument that recognizes different modes of
arguing further expands the realm of argument, in a way that makes the
analysis of argument bear on a much broader range of reasoning. Modes
are typically defined in a manner which highlights and draws attention
to the different kinds of components which may be used in building
arguments. Some have suggested that it is important to distinguish
between modes of spoken and written arguing because the sound of a
speakers voice is a key ingredient of the former which has no exact
equivalent in the latter. Making this distinction is one way to
recognize the important role that an accent, a scream, a sobbing tone,
or other prosodic elements may (as Kišiček forthcoming
shows) play in argument.

The idea that there are different modes of arguing is one way to
account for new forms of argument that the development of
communication technology makes possible. Virtual reality is, for
example, emerging as a powerful vehicle for political argument. One of
the first VR productions by the New York Times is
“Kiya,” which recreates an incidence of domestic abuse in
order to demonstrate the need to address the issue of domestic
violence. Its producer describes it as an attempt to use “the
immersive power of virtual reality: its ability to generate intense
empathy on the part of the viewer; to wring from the audience the
intense emotional connection that these stories deserve” (NYT,
Jan 21, 2016). In constructing arguments, this kind of emotional
connection can be a key element of the attempt to successfully
convince an audience of some conclusion.

2.4 Coalescent Argument

Extending the notion of argument so that it encompasses different
modes of arguing can be done without giving up the evidentiary notion
of argument or the idea that evidence is presented in a set of
premises that support some conclusion. One finds a more radical
approach to the definition of argument in the work of Gilbert 1997,
2014 (cf. Carozza 2007). According to his account, arguing occurs when
clusters of attitudes, beliefs, feelings and intuitions produce
disagreement. An argument is an attempt to identify the points of
agreement that characterize different arguers, in a way that brings
together (the “coalescence” of) their different points of
view. This approach expands the scope of argument to include whatever
can be used to bring about the coalescence that is the aim of
argument. This allows the substance of argument to be, not only
reasons in the traditional sense, but also emotional or physical or
other means of coalescence.

Gilbert develops his account by recognizing argument as it is
traditionally conceived as the “logical” mode of argument,
and by adding to it “emotional,” intuitive
(“kisceral”), and physical (“visceral”) modes
of argument. According to this account, a hug, a forlorn look, or
tears may count as argument. In real life situations, this underscores
the point that they may be a more effective method of resolving
disagreement than premises as they have been traditionally

When we analyze real life arguments, our first task is the
identification of its component parts. Following Woods 1995b, doing so
is sometimes called the “dressing” of an argument. This
invokes a comparison with the butcher’s craft, where one takes animals
“on the hoof” and dresses them to produce meat for
consumption. In the case of arguments, arguments on the hoof are
arguments as they appear in their real life contexts. One dresses them
to identify and isolate their key components in a way that prepares
the way for argument evaluation. Depending on the circumstances, and
how extensive an analysis one wants to carry out, the following are
key aspects of an argument that may need to be identified in the
process of dressing it.

3.1 Premises and Conclusions

The most obvious task in dressing an argument is the identification of
its premises and conclusion. Whether one analyzes an argument from a
formal or an informal point of view, this is the starting point for
argument evaluation. Like formal logic, informal logic understands
premises and conclusions as the core components of an argument. In
simple cases, they are clearly and explicitly indicated and easily

Dressing arguments is a key aspect of the analysis of arguments that
occur in ordinary discourse because such arguments are frequently
unclear or open to interpretation. In isolating their premises and
conclusions this means that we may have to:

  • discard irrelevant digressions and off hand remarks
  • eliminate rhetorical questions and other stylistic devices that
    obscure their meaning;
  • pick between alternative ways of expressing them;
  • settle the issues raised by incomplete, vague or ambiguous claims
    and utterances; and
  • (to the extent that one recognizes different modes of arguing)
    identify visual, auditory, olfactory and other kinds of premises that
    provide evidence for a conclusion.

The analysis of examples in this article illustrates how this can be
done in a wide variety of cases.

3.2 Implicit Premises and Conclusions

The possibility of implicit (sometimes called “hidden”)
premises or conclusions is already recognized in ancient times, most
notably in the discussion of enthymemes. Some examples have already
been noted. Another is the following argument, by then American
Vice-President Dick Cheney, defending the decision by the Bush
administration to try foreigners charged with terrorism offenses in
tribunals located outside the United States — locations not
encumbered by protections of the accused guaranteed in American

EXAMPLE 8 (from a report in the New York Times, 15/11/2001):

“The basic proposition here is that somebody who comes into the
United States of America illegally … is not a lawful combatant….
They don’t deserve to be treated as a prisoner of war.”

We can plausibly summarize this argument as:


Premise: Somebody who comes into the United States of America
illegally … is not a lawful combatant.

Implicit Premise: Someone who is not a lawful combatant
doesn’t deserve to be treated as a prisoner of war.

Inference (Premise) Indicator: “The basic

Conclusion: They don’t deserve to be treated as a prisoner of

Here the implicit premise identifies the link that ties the explicit
premise to the conclusion. In dressing the argument it needs to be
made explicit because it needs to be assessed in any attempt to
evaluate the argument. Recognizing it raises the question how a
“lawful combatant” should be defined, especially as
combatants who illegally enter a country for the purpose of war (in
undertaking surveillance or going behind enemy lines, for example) are
widely recognized as prisoners of war.

The task of identifying implicit premises or conclusions raises
theoretical questions because there are many circumstances in which
different implicit premises or conclusions can be attributed to an
argument. One common principle used in such circumstances is the
“Principle of Charity,” which directs us to look for an
implicit component premise that makes the argument as strong as
possible. An alternative approach ascribes an argument the
“logical minimum” — i.e. the weakest premise necessary in
order to connect the argument’s premises to its conclusion.

3.3 Audiences

A full account of the components of an argument must recognize aspects
of their external as well as their internal components. In ordinary
discourse, arguments often function as a way to convince a specific
audience of some point of view, making audience a key feature of the

A successful argument for the conclusion that the United Nations
should be supported will, for example, need to address different
issues when it is directed at a Chinese, Norwegian, or Swiss audience.
As successful arguers have always known (and as rhetoric emphasizes)
successful arguers address the beliefs, attitudes and values of their
intended audience (they in this sense‘speak’ to it). In
the world of actual argument, this frequently means that true premises
and a valid inference are not sufficient for successful argument. This
is why Tindale (1999, 2004, 2010) and others advocate an approach to
informal logic that incorporates the analysis of audience.

The simplest way to build audience into the analysis and assessment of
informal argument is in the way Aristotle suggests in his
Rhetoric. Taking his approach, we must evaluate an argument
not only by considering its logical strength (its logos, but
also the pathos of the audience to whom an argument is
addressed, and the character (the ethos) of the arguer as it
impresses itself on the audience. The latter because, as Aristotle
says, an audience will be more easily convinced by someone who they
perceive to be a good person.

3.4 Kinds of Dialogue

Another external component of arguments is the kind of dialogue in
which they are embedded. In a dialogue of inquiry, arguments are used
as tools in an attempt to establish what is true. So understood,
arguments must adhere to strict standards that determine what counts
as evidence and counter-evidence for some point of view. In
negotiation dialogue, arguments function in a different way. Here the
aim is an agreed settlement between two parties who have conflicting
interests and different, possibly irreconcilable, points of view. One
can summarize these differences by saying that the expectations, norms
and procedures for arguing depend on the kind of dialogue in which an
argument is proposed.

Walton 2007 understands a dialogue as an exchange made up of an
opening stage, an argumentation stage, and a closing stage. In the
opening stage, the arguers in the dialogue agree to participate. The
rules for the dialogue define what types of moves are allowed, what
kinds of questions and responses are permitted, and what norms must be
adhered to. The seven basic types of dialogue he distinguishes can be
summarized as follows.

Type Situation Arguers’ Goal Dialogue Goal
Persuasion Conflict of Opinion Persuade Other Party Resolve Issue
Inquiry Need to Have Proof Verify Evidence Prove Hypothesis
Discovery Need for Explanation Find a Hypothesis Support Hypothesis
Negotiation Conflict of Interests Secure Interests Settle Issue
Information Need Information Acquire Information Exchange Information
Deliberation Practical Choice Fit Goals and Actions Decide What to Do
Eristic Personal Conflict Attack an Opponent Reveal Deep Conflict

Within these general categories, more specific kinds of dialogue may
be governed by strict rules. One subspecies of negotiation dialogue
is, for example, collective bargaining, which legally prohibits
“bargaining in bad faith” — i.e. bargaining which takes
place outside the bargaining table. In this kind of negotiation, the
use of threats (to strike or lock employees out) are a key part of the
process. In sharp contrast, threats are not acceptable in critical
inquiry, where they are classed as instances of the fallacy ad

The question whether there are other kinds of dialogue which need to
be recognized remains open, as does the question whether there are
types of argumentation which cannot be categorized in terms of any of
the standard forms of dialogue (because they are a hybrid of different
kinds of dialogue, or some new form of dialogue which is not clearly
defined). Recognizing a dialogue in which an argument is embedded is
an important part of dressing when this imposes standards for
argumentative exchange which arguers may not have properly adhered

3.5 Dialectical Objections

Dialectics highlights the extent to which argumentation is an exchange
between (real or imagined) interlocutors who argue for opposing points
of view. It positions argument within the broader scope of dispute and
debate. In argumentation theory, this approach to argument has been
highlighted in pragma-dialectics, a theory which originates in Van
Eemeren and Grootendorst 1992. It has been elaborated by “the
Amsterdam School”, which has extended the different aspects of
their theoretical perspective (see Feteris et al. 2011). It
understands argumentation as a means of resolving differences of
opinion according to the rules of critical discussion (a particular
kind of dialogue that aims at the rational resolution of differences
of opinion).

Within informal logic, the dialectical aspects of argument are
manifest in the notion that arguers have “dialectical
obligations” which are an essential component of proper argument
(see Johnson 2000). As arguers, this suggests that our fundamental
dialectical obligation is an obligation to respond to (and, where
possible, anticipate) alternative points of view. In particular, we
must respond to objections to our own views that are likely to be
raised by our opponents in the dispute in which we are engaged.

To emphasize this point, Johnson distinguishes between the
“illative” core of an argument and its
“dialectical” tier. The illative core is the set of
premises offered in support of the conclusion; the dialectical tier
consists of alternative points of view, likely objections to the
conclusion, and the premises and whatever assumptions characterize
debate about the conclusion. According to Johnson, all genuine
arguments are dialectical and all arguers are obligated to discharge
dialectical obligations. This suggests that the standard account of
argument assumed in the history of logic — a giving of reasons
for some conclusion — can, without such elaboration, be
classified only as a “proto-argument.”

Whether or not one goes as far as Johnson, one of the external
components of argument that needs to be taken into account in dressing
many real life arguments is the extent to which it is dialectical and
the objections of interlocutors (real or potential) who have different
points of view. This is another aspect of argument which may need to
be noted in preparing it for assessment.

3.6 From Dressing to Assessment

Dressing arguments is a precursor to argument evaluation. It aims to
identify and isolate their premises and conclusions, the inferences
they contain, and other components which may be relevant to their
assessment. Dressing can be a complex endeavour which requires the
discarding of irrelevant aspects of communication, an interpretation
of a situation in which premises and conclusions are not clearly
demarcated, the identification of implicit premises or conclusions;
and/or a recognition of multimodal premises or conclusions. In many
cases, it requires a recognition that it is embedded in a particular
kind of dialogue, is part of an exchange with some identifiable
argumentative opponent, or is addressed to a specific audience an
arguer is trying to convince. In this way, a full dressing of an
argument requires a detailed account of its internal and external

As Blair 2015 has emphasized, the ultimate goal of informal logic is
normative. Its aim is an account of argument that can be used to
decide when arguments are strong and weak; good and bad; and plausible
and implausible. Informal logicians dress arguments to prepare them
for evaluation. In view of this much of informal logic is an attempt
to develop standards, criteria and processes for judging arguments.
Particular arguments may be assessed in terms of general criteria for
good argument; or as an instance of a fallacy or a particular scheme
of argument.

One way to assess arguments in ordinary discourse is by translating
them into a formal language and assessing them accordingly. This is a
method which informal logicians sometimes use, especially in
discussions of artificial intelligence, game theoretic approaches to
dialogue, and formal accounts of various kinds of reasoning. More
informal methods have been emphasized in the teaching of arguments and
reasoning. in the use of informal logic in public discourse (to argue
for or against, or in the analysis of particular points of view) and
in the study of arguments which are not easily accommodated by formal

4.1 AV and ARS criteria

In classical logic, an argument is (deductively) valid if its
conclusion follows from its premises — if it is impossible for its
premises to be true and its conclusion false. The ultimate aim of
arguing is a “sound” argument: a valid argument with true
premises. Many issues arise if one tries to apply these criteria to
informal arguments without adapting them in a number of ways, but they
usefully make the point that the strength of an argument is a function
of two things: (i) the viability of its premises, and (ii) the
strength of the inference from these premises to its conclusion.

Within informal logic the simplest criteria for judging arguments is
an informal analogue of soundness. It requires that an argument’s
premises be acceptable and that its conclusion follow from these
premises. We may call the latter “informal” validity
(leaving open the question how it is best understood) and these two
criteria the “AV” (Acceptability, Validity) criteria for
assessing arguments.

Following Johnson & Blair (1977, 1994) many informal logicians
understand informal validity in terms of relevance and sufficiency,
making the criteria for good argument acceptability, relevance and
sufficiency (the “ARS” criteria). The premises of an
argument count as relevant to its conclusion when they provide some
support for the conclusion and sufficient when they provide enough
support to establish it as plausible. Relevance can be contrasted with
irrelevance, which occurs in various instances of non
, as occurs in the case of “straw man” and
“red herring” arguments, which are common in ordinary

In contrast with classical logic, both the AV and ARS criteria assess
premises as acceptable or unacceptable rather than true or false.
Informal logic evaluates premises in this way for many reasons. As
Pinto 2001 points out, the aim of many arguments does not appear to be
assent to the truth of a proposition but the withholding of assent (or
full assent) or a particular attitude or emotional state. An argument
may, for example, function as a means of instilling fear or hope or
disapprobation. In order to leave room for these kinds of examples, he
defines an argument as “an invitation to inference”
(68–69) which need not have as its aim justifying the truth of
some proposition.

Informal logic favors acceptability over truth as a criteria for
judging premises for other reasons as well. Because real life arguing
tends to take place in contexts characterized by uncertainty which
make it difficult to make judgments of truth or falsity. Because such
arguments frequently revolve around ethical and aesthetic judgments
which are not easily categorized as true or false. Because there are
contexts (e.g., bargaining) in which good arguments do not depend on
premises that can clearly be categorized as true or false. Because
there are other contexts (in dealing with specific audiences, e.g.) in
which truth may not, in itself, make a premise acceptable for informal
argument. And, more generally, because philosophical discussions of
truth which have raised many questions about what counts as true and

Understanding argument strength in terms of truth is also problematic
in case of multimodal arguments which employ images and other
non-verbal kinds of evidence. In these kinds of cases, it is not
difficult to understand multimodal elements (photographs, diagrams,
etc.) as misleading or not (and hence acceptable or unacceptable)
though they are not naturally described as true or false.

4.2 Natural Language Deductivism

Within argument evaluation, one of the key questions raised by
informal logic is the question how we should understand the informal
validity which is a key component of strong arguments. Though informal
logicians commonly distinguish between deductive and various
alternative kinds of validity, some have (as Govier 1987 points out)
assumed an alternative view, which she calls “Natural Language
Deductivism” (NLD). It maintains that all informal arguments can
best be interpreted as attempts to create deductively valid
inferences, and should be analyzed and assessed accordingly.

To understand how NLD operates, we must see past the traditional use
of deductive proof in logical and mathematical reasoning, which has
encouraged the common misconception that deductive arguments are
arguments with certain or necessary conclusions (like those
traditionally associated with logical and mathematical reasoning). In
general, a deductive conclusion is as certain as the premises it is
founded on. This is an important point in informal contexts, where
arguments rely on premises which are reasonable or plausible rather
than certain. In such contexts, deductive arguments yield conclusions
which are not certain, but reasonable or plausible.

The following example is taken from a radio commentary on population


The population of the world will grow from 6 to 9 billion in the next
fifteen years so we will, if we are to provide sufficient food for
everyone, need a way to provide for an additional 3 billion people.

This is an obviously deductive argument but one which depends on a
premise which is not certain, but reasonable (because it is backed by
other reasoning that extrapolates from established population trends).
The argument is deductively valid, but it follows that its conclusion
is reasonable rather than certain.

In dealing with arguments which are not explicitly deductive, the NLD
approach interprets an argument as a deductive argument by attributing
it implicit premises that make it so. The following argument is a
frequently criticized pattern of popular reasoning which appeals to
the authority of the television personality Dr. Oz, who provides
nutritional and lifestyle advice.


Dr. Oz Says It, So It Must Be True

If one judges only by the explicit premise (“Dr. Oz Says
It”) this is not a deductively valid argument for the premise
could be true and the conclusion false (Dr. Oz could be wrong). NLD
circumvents this issue by ascribing the argument an implicit premise
which renders it deductive. So understood the argument can be
summarized as:


Premise: Dr. Oz Says It.

Implicit Premise: If Dr. Oz says it, it must be true.

Inference Indicator: “So” (conclusion indicator)

Conclusion: It must be true.

This is a plausible reconstruction of the argument. For we cannot draw
the conclusion from the stated premise without accepting the implicit
premise. Once it is explicit, the argument is a clearly deductive.
This does not make it a good argument and instead suggests that we
must evaluate its strength, not by evaluating its validity, but by
evaluating the plausibility of its premises. Because the implicit
premise is implausible — as could be shown by citing many examples
where Dr. Oz’s advice can be shown to be questionable — an NLD
analysis entails the (correct) conclusion that the argument is

Because NLD reconstructs informal arguments as deductively valid
arguments, Govier describes it as a theory of
“reconstructive” deductivism. It makes argument assessment
a two step process which (i) reconstructs an argument (by adding
implicit premises) to make it a clearly deductive inference, and (ii)
then evaluates the argument by assessing the strength of its (explicit
and implicit) premises. The pragma-dialectical account of indirect
speech acts (Eemeren and Grootendorst 2002, Groarke 1999) is well
suited to the first of these two tasks. Deductive reconstruction
always seems possible because one can always assign the claim that an
argument’s conclusion follows from its explicit premises as an
implicit premise that renders the inference deductively valid.

The following inductive generalization can serve to show how NLD deals
with what would otherwise be thought to be paradigm examples of
informal arguments which are not deductively valid.


The French are fastidious about their appearance. I have met many of
them in the course of my work there and this was true of all of them.

Taking an NLD approach, this argument can be understood as a
deductively valid argument which can be dressed as:


Premise:I have met many French in the course of my work there
and all of them were fastidious about their appearance.

Implicit Premise: The French have the attitude I witnessed in
the many French I have met.

Inference Indicator: therefore (implicit)

Conclusion: The French are fastidious about their appearance.

When the argument is analyzed in this way, its strength can be
evaluated by assessing the strength of its explicit and implicit
premise. This is a productive approach to evaluation because the
fundamental issue the argument raises is whether the French the arguer
has met are a representative sample of the French in general (rather
than, say, those in their own profession), i.e. the question raised
when one assesses the proposed implicit premise.

Deductivist reconstruction is an approach to argument assessment which
makes explicit some of the key claims and assumptions that individual
arguments depend on. Because it analyzes all arguments as instances of
one well understood form of inference it eliminates the need to
distinguish between arguments which are deductive, inductive,
conductive, abductive, etc. — a distinction which can be difficult to
make in dealing with informal arguments which can be interpreted in
different ways. Aristotle is a key figure who adopts a deductivist
approach (see Groarke 2009).

Those who reject deductivism argue that it is an artificial theory
which forces informal arguments to adhere to an overly restrictive
model of inference that is too narrow to account for the richness of
ordinary reasoning (see Johnson 2000 and Godden 2004).

4.3 Informal Validity in Other Guises

Other approaches to informal logic understand informal validity in a
variety of ways. They see deductive reasoning as one variant of such
validity, but distinguish other ways in which premises may entail
conclusions. In doing so, they assess the strength of an argument by
assessing the acceptability of its premises and the strength of the
link between its premises and its conclusion. The ARS criteria provide
one basic way to distinguish between arguments that provide no, some
and strong support for their conclusions.

Many treatments of informal arguments assume the distinction between
deductive and inductive arguments, a distinction which Govier 1987
dubs “the great divide,” emphasizing the latter over the
former. Sometimes inductive arguments are understood narrowly, as
inductive generalizations, but are more commonly said that to be
arguments in which the premises of the argument only probable or
plausible, leaving open the possibility it is false.

In their categorization of basic forms of inference, informal logic
also countenances other forms of validity: notably
“conductive” and “abductive” arguments.
Conductive arguments accumulate non-decisive reasons in favour of a
conclusion. Different pieces of evidence may merely suggest (and not
prove) that someone charged with murder is guilty. But accumulated
(the witness said he pulled the trigger, the ballistics report shows
that the bullet came from a gun he owned, he was overheard saying he
would “get” the victim, etc.) these different reasons may
provide a strong, though not conclusive, conductive argument for the
conclusion that the accused is guilty.

Abductive arguments are inferences to the best explanation. They
typically recognize some facts, point out that they are entailed by
some hypothesis, and conclude that the hypothesis is true. Taken at
face value, abductive arguments appear to be instances of the
deductive fallacy “affirming the consequent,” and might on
these grounds be dismissed, but it is clear that they play a central
role in medical, scientific and legal reasoning (see Walton 2004).

4.4 Fallacy Theory

In its search for more nuanced ways to deal with informal logic,
informal logic initially turned to fallacy theory. In its treatment of
the fallacies, it revives a tradition which can be traced to
Aristotle. In the history of logic and philosophy, its significance is
reflected in the writings of Locke, Whately, and Mill. Today, this
tradition manifests itself in textbooks and websites which attempt to
teach good informal reasoning by teaching students how to detect the
standard fallacies. One can find a detailed discussion in the article
in this encyclopedia.

Theoretical discussions of fallacies have not produced an agreed-upon
taxonomy, but there is a common set of fallacies which are frequently
used in the analysis of informal arguments. They include formal
fallacies like affirming the consequent and denying the antecedent;
and informal fallacies like ad hominem (“against the
person”), slippery slope, ad bacculum (“appeal to
force”), ad misericordiam (“appeal to
pity”), “hasty generalization,” and “two
wrongs” (as in “two wrongs don’t make a right”). In
informal logic textbooks, authors may devise their own nomenclature to
highlight the properties of particular instances of fallacious
argument (“misleading vividness” designates the misuse of
vivid anecdotal evidence, and so on.)

In the research literature, Woods and Walton have discussed the
definition, analysis and assessment of a variety of fallacies in a
series of articles and books, first as co-authors and then
individually (see Woods and Walton 1989, Walton 1989, Woods 1995,
Walton 2000). Van Eemeren and Grootendorst 1992 have proposed a
“pragma-dialectical” theory which analyses fallacies as
violations of the rules of critical discussion dialogues. A
representative collection of classical and contemporary essays on the
fallacies is found in Hansen and Pinto 1995.

Fallacy theory has been criticized on the grounds that there is no
agreed way to define what a fallacy is; because there is considerable
disagreement over the definition of particular fallacies; and because
one may evaluate most arguments without having to rely on an account
of fallacies (see, e.g., Feldman 2009). Approaches to ordinary
argument that do focus on fallacies emphasize examples of poor
reasoning rather than good argument. Hitchcock (1995, 324), e.g.,
writes that the idea that we should teach reasoning by fallacies is
“like saying that the best way to teach somebody to play tennis
without making the common mistakes … is to demonstrate these
faults in action and get him to label and respond to them.”

The issues with fallacy theory are compounded by many instances of
traditional fallacies which seem to have some merit real life
argument. The following are examples:


A remark from a Danish television debate over the question whether the
Danish church should be separated from the Danish state (Jorgensen
1995, 369): “You should not listen to my opponent. He wants to
sever the Danish church from the state for his own personal
sake.” This appears to be a classic example of ad
, Kahane 1995 (p. 65), describing it as a fallacy that
occurs when an arguer attacks “his opponent rather than his
opponent’s evidence and arguments.” In this case the issue
raised is the speaker’s motivation for his position rather than the
position itself. But if there is good reason to believe that he wants
to sever the church from the state for his own personal gain, this may
be a legitimate reason not to take his arguments seriously (because he
has a conflict of interest).


Martin Luther King Jr., influenced by Gandhi, argued that we can
justifiably break laws if our goal is just change. Such arguments play
a central role in the civil rights movement. They are not obviously
fallacious, but they seem to be a clear case of “two wrongs make
a right” suggesting that we can justifiably do something wrong
(break a law) because it is a response to another wrong.


The argument that “the attempt to use military might to put an
end to terrorism is wrong because it will take us down a slippery
slope that will end in improper interference in the affairs of
independent states” cannot be dismissed by saying that it is an
instance of the fallacy slippery slope. If the slippery slope is
plausible, then the argument has some merit.


The argument “No one with a history of heart disease should take
up running, for running is a strenuous form of exercise, and no one
with a history of heart disease should engage in strenuous
exercise” is deductively valid. One cannot accept the premises
without accepting the conclusion. But this suggests that all deductive
arguments commit the fallacy begging the question, which occurs when
an argument assumes what it attempts to prove.

In the wake of many examples and discussions of this sort, careful
accounts of fallacies increasingly recognize that there can be
reasonable arguments which have the form of traditional fallacies.

One way to deal with the issues such examples raise is by
distinguishing fallacies which do and do not have non-fallacious
instances. Equivocation, post hoc ergo propter hoc, false
dilemma, non sequitor and hasty generalization are, for
example, patterns of argument that are inherently mistaken. In
contrast, fallacies like ad hominem, two wrongs reasoning,
guilt by association, and appeal to pity are fallacies which appear to
have legitimate uses in real life reasoning.

If one analyzes ad hominem as a particular kind of move in
dialectical exchange, for example, then one may recognize rules of
dialogue which distinguish circumstances in which such moves are and
are not acceptable.

Though some of the issues with the traditional fallacies have
diminished their significance in the theory of argument, they continue
to be a popular way to analyze everyday reasoning and argument,
introductions to fallacies sometimes listing hundreds of variants
(Dowden 2016 (Other Internet Resources), Bennett 2013, Paul and Elder
2012). Battersby and Bailin 2011 have suggested that fallacies be
understood as argument patterns “whose persuasive (rhetorical)
power greatly exceeds its probative value (i.e., evidential
worth),” making fallacies errors in reasoning that are rooted in
their rhetorical appeal.

4.5 Argument Schemes

Argument schemes are recurring patterns of argument. Once identified
they can be used to evaluate an instance of arguing, or as recipes
which tell us how to construct strong arguments. Walton, Reed &
Macagno 2008 provide a significant compendium of 96 schemes. Within
informal argument, commonly used schemes include Argument by Sign,
Argument by Analogy, Argument by Example, and Slippery Slope

One standard approach to argument schemes combines a particular
pattern of argument with a set of “critical questions”
that it raises. Consider the scheme “Appeal to Authority”
(also called “Appeal to Expert Opinion”), which might be
summarized as 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?

The following student comment is an example of an argument from


We should not stockpile nuclear weapons. We need to heel Einstein’s
warning, after the bombing of Hiroshima, that the proliferation of the
atom bomb would inevitably lead “to destruction even more
terrible than the present destruction of life.”

We can summarize this as an instance of the argument from authority
scheme, where A=Einstein, D=politics (of nuclear weapons), T=The
proliferation of nuclear weapons will lead to terrible destruction. We
can then assess the argument by asking whether there are satisfactory
answers to the critical questions the argument raises. In this case,
questions of particular importance are question 2 (“Is Einstein
an authority on the politics of nuclear weapons?”) and question
5 (“Is the claim that the proliferation of nuclear weapons will
lead to terrible destruction with what other experts on the politics
of nuclear weapons assert?”). Because it is not clear that
either question has a positive answer, example 16 is a weak

One way to understand schemes is as moves in argument which are backed
by the warrants implied by the critical questions that accompany them.
Alternatively, one may understand a scheme as a kind of inference rule
(see Prakken 2010b), some critical questions ensuring the truth of the
premises, others ensuring that the context of the inference is
appropriate. Deductive schemes are commonly codified in standard rules
of inference like modus ponens (“Affirming the
Antecedent”), double negation, modus tollens, etc.

Groarke & Tindale 2013 use traditional fallacies as a basis for a
set of schemes, treating ad hominem, guilt by association,
appeals to ignorance, two wrongs reasoning, etc. not as fallacies, but
as legitimate patterns of reasoning. If an arguer has, for example,
repeatedly shown poor judgment, bias or clearly lacks the requisite
knowledge to make reasonable judgments about some issue, then this is
a plausible reason to dismiss their point of view on ad
grounds. This is especially true in informal contexts, in
which arguers frequently do not have the time or ability to
investigate and assess all the arguments behind the various positions
directed at them. On this account of schemes, fallacies turn out to be
deviations from an inherently correct norm.

4.6 Multimodal Argument

Much remains to be said about the assessment of multimodal arguments
that include non-verbal elements. That said, the different techniques
informal logic uses to assess informal arguments can in many cases be
applied to visual and other multimodal arguments. Even when the
premises of an argument are not verbal, one can judge them as
acceptable or not. A photograph or an image presented as evidence for
a conclusion may be unacceptable because it presents a situation in a
misleading way — because it cuts out essential context, because it
has been tampered with, and so on. In advertising, many photographs
are purposely ‘doctored’ to present things in ways that do not
accurately reflect what is photographed.

In evaluating multimodal argument, the AV and RSA criteria for good
argument can be applied. In an election campaign, a political cartoon
which depicts a politician as a liar may invite the inference that
voters should not vote for him/her. In assessing the argument
presented, we may ask whether this portrayal fairly or unfairly
characterizes the politician in question, and whether the suggested
conclusion that one should not vote for them follows (possibly not if
other candidates have more serious shortcomings).

In many instances, multimodal arguments are instances of fallacies of
particular argument schemes. Visuals used in argumentation are, for
example, often instances of “hasty generalization,” using
emotionally powerful pictures of some behavior to promote
generalizations which are not founded on a proper, representative
sample. Dove 2016 has discussed the application of argument schemes to
cases of visual argument, showing how this is easily accomplished. He
suggests one scheme, “argument from fit” as a uniquely
visual scheme that applies to arguments in which the borders of two
objects are visually inspected to determine whether the objects are
part of a larger whole (as when one tries to piece together fragments
one might find in an archaeological dig).

Like any field of study, informal logic is constantly evolving. Its
attempt to understand argument as it occurs in a broad range of real
life situations continues to push it toward a broader account of
argument which recognizes more ways in which arguing can occur and how
and when it should be judged successful. The following are some
current topics of discussion.

5.1 Argument Maps

When one understands an argument as a collection of premises and a
conclusion with an inference structure one may illuminate and analyze
this structure with argument diagrams or “maps.” Mapping
of this sort has a long history. It is already used in Whatley 1826
and in the early twentieth century, by Wigmore 1913, who develops a
form of mapping (“evidence charts”) to portray and analyze
complex chains of judicial reasoning.

As interest in the analysis of informal reasoning has intensified, it
has been accompanied by a renewed interest in argument mapping. In
some ways this has revived the practice of mapping, but in a new way
that allows for much more complex and sophisticated approaches to
mapping. Most significantly, it has been accompanied by the
development of software (Rationale, Reason!Able, Araucaria, Athena,
Compendium, Theseus) and online aids (Debate Mapper, TruthMapping.Com,
Argunet, Agora) designed to assist in the mapping of real life

5.2 Narratives in Argument

One of the catalysts for the development of informal logic has been
the desire to extend theories of argument so that they can account for
aspects of arguing which are not accounted for in traditional accounts
of argument. The study of the argumentative use of visuals
(photographs, video, drawings, etc.) is a case in point. A more recent
topic is the study of the role of narratives in arguing. This is a
role that is already highlighted in ancient times — most famously in
Plato. His version of “The Ring of Gyges” is, for example,
a story used to support a particular conception of human nature. In
the case of fables, parables, and morality plays, narratives seem to
be explicitly designed to be effectively used in argument.

One can understand the narratives used in argument in different ways:
as embellishments, analogies, or as veiled generalizations. Current
discussions are influenced by Fisher 1987, who argues that argument
itself is best understood as narrative, and by Nussbaum 1990, who
looks to literature as a way to better understand complex moral
situations. The significance of narratives in arguments is recognized
in argument schemes that Walton, Reed, & Macagno 2008 identify as
“narrative-based” schemes.

But the extent and usefulness of analyses of narratives as argument
remains a matter of debate (see Govier & Ayer 2013, Olmos 2014,
Plumer 2015). Certainly it is clear that stories, including fictional
stories, can play a key role in establishing conclusions, but this
leaves open the questions whether they should be understood as
premises and/or conclusions, and whether they are in some way
irreducibly narrative (and need to be analyzed and evaluated with
alternative standards for good argument).

5.3 Argument Flags

It seems obvious that an argument cannot succeed without being
recognized and paid attention to. The best argument in the world
cannot convince someone of its conclusion if everyone ignores it. In
the world of public argument, this is a serious issue, for the public
has a great many arguers and arguments competing for its attention. In
a world in which a quick search for information produces thousands of
competing arguments on virtually any topic, it is constantly
overwhelmed by many more arguments and points of view than anyone can
consider seriously.

Argument “flags” operate as one solution to this problem,
functioning as a way to draw attention to an argument. A successful
flag may be a stunning photograph of a tragedy, a provocative act (of
the sort that draws attention to Greenpeace campaigns), a large
newspaper headline, or a question that peaks an audience’s curiosity.
Many flags are not a part of the premise and conclusion structure of
an argument, only serving to draw attention to it. In cases such as
these, a flag does not add to the epistemic merit of an argument, but
it may still play a key role achieving argument success by ensuring
that an argument is taken seriously.

5.4 Emotions in Argument

Traditionally, emotional appeals have been seen as fallacious moves in
argument. This is too simple a view of the role of emotion within
informal discourse, where appeals to emotion play a significant role
that cannot be rejected out of hand. In a discussion of nuclear
policy, the emotion inherent in a description of the consequences of
nuclear war (say, the dropping of the bomb on Hiroshima) can play a
legitimate role in argument. In legal proceedings, there is explicit
room for a victim’s emotional account of the impact of a crime, which
is usually considered in sentencing.

Gilbert 1997,2014 has emphasized emotional arguments, investigating
the role that different kinds of emotion and expressions of emotion
play in real life arguments, where they often function as a way to
convince an audience of a particular point of view. When a student (to
take one of Gilbert’s examples) cries in a professor’s office as they
plead for a higher mark, their emotional outpouring is a key component
of their attempt to convince the professor that their mark should be
changed. In real interchange, such appeals are frequently successful.
In distinguishing between appeals which should be accepted and
rejected, Gilbert suggests a re-conception of argument that recognizes
emotional arguments as a unique genre of argument that needs to be
evaluated in a different way than traditional approaches to argument

5.5 Critical Thinking Tests

Critical thinking tests attempt to measure argumentation skills. They
have been used to test the abilities of students or others, but also
as a way to test the success of attempts to teach informal reasoning.
Though they can provide an important way to empirically measure the
skills that informal logic teaches, many of the tests are inconclusive
and beset by many problems.

What should count as good reasoning and critical thinking (or, even
more so, creative thinking) is not easily assessed using standardized
tests designed for large scale use, which typically rely on multiple
choice question and answers (see Sobocan et al. 2007). The California
Critical Thinking Test reflects the (outdated) view of critical
thinking elaborated in “The Delphi Report,” commissioned
by the American Philosophical Association in 1987. It focuses on a
very narrow range of critical thinking skills (one of many
possibilities) which in many ways oversimplifies the competencies
required for good informal reasoning (see Groarke 2007).

In real life contexts, good arguing (and thinking) is in many ways
open ended and unpredictable, dialectical, and influenced by pragmatic
and contextual considerations which are difficult to incorporate
within standard tests. Ennis 2013 provides a comprehensive proposal
for dealing with this and the other complex issues that are raised by
attempts to teach critical thinking.

5.6 Argument Mining

The assumptions of informal logic have been tested in a different way
by commentators who study argument “corpora” — large
collections of argument drawn from natural language discourse. In an
early study of this sort, Jorgenson, Kock and Rorbech 1991 analyzed a
series of 37 one-hour televised debates from Danish public TV. The
debates featured well-known public figures arguing for and against
current policy proposal. A representative audience of 100 voters voted
before and after the debate, in an attempt to statistically establish
what moves and properties are likely to win votes in a representative
audience. These conclusions were then compared with commonly held
notions about “proper” or “valid”
argumentation. Other studies consider corpora made up of large
databases of selected written texts (see, e.g., Goodwin & Cortes
2010, and Mochales & Ieven 2009). In principle, corpora made up of
whole libraries may be tested.

Argument mining has emerged as a subfield of data mining, or text
mining (or computational linguistics). It uses software and algorithms
that automatically process text looking for argument structures — for
premises, conclusions, argumentation schemes, and extended networks of
argument. Researchers have investigated methods for argument mining in
legal documents , on-line debates, product reviews, academic
literature, user comments on proposed regulations, newspaper articles
and court cases, as well as dialogical domains.
the Centre for Argument Technology, plays a central role in such

5.7 Virtue-based Approaches to Argument

Virtue-based approaches to informal argument extend virtue-based
approaches to ethics and epistemology to the realm of informal
argument. Doing so shifts attention from a focus on acts or objects of
arguing toward the agents who create them. Looking at arguments from a
virtue point of view, one might say that the wise person (the person
who embodies virtues) is the best judge and provides the ultimate
criterion for whether something is a good or bad argument or should be
believed. This makes the epistemological criterion the lived reality
of someone judicious rather than a fixed formula or algorithm. A list
of works on virtue approaches to argument is available at
Virtues and Arguments: A Bibliography.

5.8 Artificial Intelligence (AI)

Like informal logic, the development of artificial intelligence
requires theoretical models that can account for informal arguing in
widely diverse contexts. Informal logic models of argument have,
therefore, influenced the attempt to model argumentation between
agents in multi-agent systems which mimic or assist human reasoning.
Computational applications have been applied to large-scale webs of
inter-connected arguments, and to reasoning about medical decisions,
legal issues, chemical properties and other complex systems. Automated
argument assistance functions as a computational aid that can assist
in the construction of an argument. Verheij 2014 provides a good
overview of the issues.

Insofar as informal logic remains an attempt to develop a logic that
is accessible to the everyday reasoner, it and computational modeling
will remain distinct endeavors. But both assume a theoretical
understanding of the way in which informal reasoning works and should
be assessed. In the long run, the formal modeling AI requires may
reestablish stronger links between formal and informal logic. The
results may foster the development of informal logic within a more
integrated logic (or argumentation theory) that acknowledges the
differences between formal and informal logic, but recognizes an
overarching model of argument that accounts for both.

As a field of study and research, informal logic has evolved into a
complex attempt to understand the nature and assessment of informal
arguments. Though a list of informal logic issues cannot be
definitive, the development already outlined suggest that a
comprehensive theory of informal argument (an “informal
logic”) should be made up of answers to a significant, cohesive
subset of the following questions.

  1. What are acts of arguing and what principles of communication
    which they depend on?
  2. How should non-verbal modes of arguing be understood?
  3. What different kinds of argumentative dialogue (inquiry,
    negotiation, eristic, etc.) should be distinguished? And how do they
    govern the argumentation they contain?
  4. What basic types of argument need to be distinguished?
  5. When is a premise acceptable or unacceptable?
  6. What kinds of informal validity (deductive, inductive, abductive,
    etc.) need to be distinguished?
  7. What general criteria define good argument?
  8. How should argument schema be defined?
  9. What role should fallacies play in understanding and assessing
    arguments (and how should fallacies that play a role be defined)?
  10. How do audience (pathos), ethos and other
    rhetorical notions determine successful argument?
  11. What dialectical obligations are attached to informal
  12. What is the extent to which the principles that govern informal
    argument can be incorporated within a formal systems?

Different collections of answers to these questions define
different informal logics.

To some extent, the relationship between informal logic and philosophy
flows both ways. The practice of philosophy inevitably assumes (and
often develops) some account of argument as it assembles evidence for
different philosophical perspectives. Informal logic assumes (and
often develops) some view of the nature of reason, rationality and
what counts as evidence and knowledge as it develops its theory of
argument. The philosophical issues in play are tied to complex,
unsettled questions about knowledge and evidence.

Informal logic’s ties to epistemology are reflected in Mercier and
Sperber (2011), which argues that reasoning is a practice which has
evolved from, and needs to be understood in terms of, the practice of
argumentation. Johnson 2000 pushes in the opposite direction, arguing
that a comprehensive account of argument must be built upon a
philosophical account of rationality. The account of knowledge that
Goldman 1999 develops situates it in the social interactions that take
place within interpersonal exchange and knowledge institutions. In
developing this account he pays considerable attention to informal
argument and the constraints which make it a valuable practice.
Informal logic’s relationship to the epistemological principles of
pragmatism is discussed in a 2002 volume of Philosophica
which discusses informal logic in the context of Hilary Putnam’s

Despite these overlapping interests, informal logic has had limited
influence on core philosophical disciplines. Woods 2000 speculated on
the reasons why. In part, informal logic’s position within philosophy
reflects the broader fragmentation of philosophy in North America,
Rescher 2005 (p. 4) concluding that “The most striking aspect of
contemporary American philosophy is its fragmentation. The scale and
complexity of the enterprise is such that if one seeks in contemporary
American philosophy for a consensus on the problem agenda, let alone
for agreement on the substantive issues, then one is predestined to
look in vain.” In a context characterized by increasingly
independent subdisciplines rather than shared interests, Rescher (p.
9) notes that “The rapid growth of ‘applied philosophy’ …
is a striking structural feature of contemporary North American
philosophy.” Informal logic is one aspect of this growth.

To some extent, informal logic’s relevance to philosophy does not lie
in its influence on key philosophical disciplines so much as their
influence on it. In North American and elsewhere, informal logic is a
field in which philosophers apply their theories of argument
(rationality, knowledge, etc.) to everyday argument. In keeping with
this, philosophers continue to be the core contributors to informal
logic, and philosophy departments in colleges and universities are the
core department which teach the courses which are informal logic’s
focus. The influence of these courses on enormous numbers of students
requires that we at least qualify Rescher’s remark (p. 22) that:
“The fact is that philosophy has little or no place in American
popular (as opposed to academic) culture… …philosophy
nowadays makes virtually no impact on the wider culture of North

Outside of philosophy, informal logic has been increasingly influenced
by — and has exerted its own influence on — Rhetoric, Communication
Studies, Discourse Analysis, Semiotics, Linguistics, and Artificial
Intelligence. Inside and outside of philosophy, its attempt to build a
comprehensive theory of reasoning and argument has important
implications for our view of rationality, the nature of the mind and
its processes, and the social, political and epistemological role of
reasoning and argument. At this point, explorations of its
implications for philosophy of mind, ethics and epistemology remain
rare and its focus continues to be the development for a broad theory
of argumentation that can be a basis for the analysis and assessment
of argument in a much broader range of contexts than those that have
characterized traditional logic. Its growing relationship to
computational modeling aims to provide this in a formal as well as
informal way, in machine as well as human reasoning.

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