Two competing conceptions of fallacies are that they are false butpopular beliefs and that they are deceptively bad arguments. These wemay distinguish as the belief and argument conceptions of fallacies.Academic writers who have given the most attention to the subject offallacies insist on, or at least prefer, the argument conception offallacies, but the belief conception is prevalent in popular andnon-scholarly discourse. As we shall see, there are yet otherconceptions of what fallacies are, but the present inquiry focuses onthe argument conception of fallacies.

Being able to detect and avoid fallacies has been viewed as asupplement to criteria of good reasoning. The knowledge of fallaciesis needed to arm us against the most enticing missteps we might takewith arguments—so thought not only Aristotle but also the earlynineteenth century logicians Richard Whately and John Stuart Mill. Butas the course of logical theory from the late nineteenth-centuryforward turned more and more to axiomatic systems and formallanguages, the study of reasoning and natural language argumentationreceived much less attention, and hence developments in the study offallacies almost came to a standstill. Until well past the middle ofthe twentieth century, discussions of fallacies were for the most partrelegated to introductory level textbooks. It was only whenphilosophers realized the ill fit between formal logic, on the onehand, and natural language reasoning and argumentation, on the other,that the interest in fallacies has returned. Since the 1970s theutility of knowing about fallacies has been acknowledged (Johnson andBlair 1993), and the way in which fallacies are incorporated intotheories of argumentation has been taken as a sign of a theory’slevel of adequacy (Biro and Siegel 2007, van Eemeren 2010).

In modern fallacy studies it is common to distinguish formal andinformal fallacies. Formal fallacies are those readily seen to beinstances of identifiable invalid logical forms such as undistributedmiddle and denying the antecedent. Although many of the informalfallacies are also invalid arguments, it is generally thought to bemore profitable, from the points of view of both recognition andunderstanding, to bring their weaknesses to light through analysesthat do not involve appeal to formal languages. For this reason it hasbecome the practice to eschew the symbolic language of formal logic inthe analysis of these fallacies; hence the term ‘informalfallacy’ has gained wide currency. In the following essay, whichis in four parts, it is what is considered the informal-fallacyliterature that will be reviewed. Part 1 is an introduction to thecore fallacies as brought to us by the tradition of the textbooks.Part 2 reviews the history of the development of the conceptions offallacies as it is found from Aristotle to Copi. Part 3 surveys someof the most recent innovative research on fallacies, and Part 4considers some of the current research topics in fallacy theory.

• 1. The core fallacies
• 2. History of Fallacy Theory
  • 2.1 Aristotle
  • 2.2 Bacon
  • 2.3 Arnauld and Nicole
  • 2.4 Locke
  • 2.5 Watts
  • 2.6 Bentham
  • 2.7 Whately
  • 2.8 Mill
  • 2.9 Sidgwick
  • 2.10 Copi
• 3. New approaches to fallacies
  • 3.1 Renewed interest
  • 3.2 Doubts about fallacies
  • 3.3 The informal logic approach to fallacies
  • 3.4 The formal approach to informal fallacies
  • 3.5 The epistemic approach to fallacies
  • 3.6 Dialectical/dialogical approaches to fallacies
• 4. Current issues in fallacy theory
  • 4.1 The nature of fallacies
  • 4.2 The appearance condition
  • 4.3 Teaching
  • 4.4 Biases
• Bibliography
• Academic Tools
• Other Internet Resources
• Related Entries

1. The core fallacies

Irving Copi’s 1961Introduction to Logic gives a briefexplanation of eighteen informal fallacies. Although there is somevariation in competing textbooks, Copi’s selection captured whatfor many was the traditional central, core fallacies.^[1] In the main, these fallacies spring from two fountainheads:Aristotle’sSophistical Refutations and JohnLocke’sAn Essay Concerning Human Understanding (1690).By way of introduction, a brief review of the core fallacies,especially as they appear in introductory level textbooks, will begiven. Only very general definitions and illustrations of thefallacies can be offered. This proviso is necessary first, because,the definitions (or identity conditions) of each of the fallacies isoften a matter of contention and so no complete or final definitioncan be given in an introductory survey; secondly, some researcherswish that only plausible and realistic instances of each fallacy beused for illustration. This also is not possible at this stage. Theadvantage of the stock examples of fallacies is that they are designedto highlight what the mistake associated with each kind of fallacy issupposed to be. Additional details about some of the fallacies arefound in Sections 2 and 3. As an initial working definition of thesubject matter, we may take a fallacy to be an argument that seems tobe better than it really is.

1. The fallacy ofequivocation is an argument which exploitsthe ambiguity of a term or phrase which has occurred at least twice inan argument, such that on the first occurrence it has one meaning andon the second another meaning. A familiar example is:

The end of life is death.
Happiness is the end of life.
So, death is happiness.

‘The end of life’ first means ceasing to live, then itmeans purpose. That the same set of words is used twice conceals thefact that the two distinct meanings undermine the continuity of thereasoning, resulting in anon-sequitur.

2. The fallacy ofamphiboly is, like the fallacy ofequivocation, a fallacy of ambiguity; but here the ambiguity is due toindeterminate syntactic structure. In the argument:

The police were told to stop drinking on campus after midnight.
So, now they are able to respond to emergencies much better thanbefore

there are several interpretations that can be given to the premisebecause it is grammatically ambiguous. On one reading it can be takento mean that it is the police who have been drinking and are now tostop it; this makes for a plausible argument. On another reading whatis meant is that the police were told to stop others (e.g., students)from drinking after midnight. If that is the sense in which thepremise is intended, then the argument can be said to be a fallacybecause despite initial appearances, it affords no support for theconclusion.

3 & 4. The fallacies ofcomposition anddivisionoccur when the properties of parts and composites are mistakenlythought to be transferable from one to the other. Consider the twosentences:

1. Every member of the investigative team was an excellentresearcher.
2. It was an excellent investigative team.

Here it is ‘excellence’ that is the property in question.The fallacy of composition is the inference from (a) to (b) but itneed not hold if members of the team cannot work cooperatively witheach other. The reverse inference from (b) to (a)—the fallacy ofdivision—may also fail if some essential members of the teamhave a supportive or administrative role rather than a researchrole.

5. The fallacy of begging the question (petitio principii)can occur in a number of ways. One of them is nicely illustrated withWhately’s (1875 III §13) example: “to allow everymanan unbounded freedom of speech must always be, on the whole,advantageous to the State; for it is highly conducive to the interestof the Community, that each individual should enjoy a libertyperfectly unlimited, of expressing his sentiments.” Thisargument begs the question because the premise and conclusion are thevery same proposition, albeit expressed in different words. It is adisguised instance of repetition which gives no reason for itsapparent conclusion.

Another version of begging the question can occur in contexts ofargumentation where there are unsettled questions about key terms.Suppose, for example, that everyone agrees that to murder someonerequires doing something that is wrong, but not everyone agrees thatcapital punishment is a form of ‘murder’; some think it isjustified killing. Then, should an arguer gives this argument:

Capital punishment requires an act of murdering human beings.
So, capital punishment is wrong.

one could say that this is question-begging because in this context ofargumentation, the arguer is smuggling in as settled a question thatremains open. That is, if the premise is accepted without furtherjustification, the arguer is assuming the answer to a controversialquestion without argument.

Neither of these versions of begging the question are faulted fortheir invalidity, so they are not charged with being non-sequitorslike most of the core fallacies; they are, however, attempted proofsthat do not transparently display their weakness. This consideration,plus its ancient lineage back to Aristotle, might explain begging thequestion’s persistent inclusion among fallacies. But, given ourallegiance to the modern conception of logic as being solely concernedwith the following-from relation, forms of begging the question shouldbe thought of as epistemic rather than logical fallacies.

Some versions of begging the question are more involved and are calledcircular reasoning. They include more than one inference. Descartesillustrated this kind of fallacy with the example of our belief in theBible being justified because it is the word of God, and our belief inGod’s existence being justified because it is written in the Bible.^[2] The two propositions lead back and forth to each other, in a circle,each having only the support of the other.

6. The fallacy known ascomplex question ormanyquestions is usually explained as a fallacy associated withquestioning. For example, in a context where a Yes or No answer mustbe given, the question, “Are you still a member of the Ku KluxKlan?” is a fallacy because either response implies that one hasin the past been a member of the Klan, a proposition that may not havebeen established as true. Some say that this kind of mistake is notreally a fallacy because to ask a question is not to make anargument.

7. There are a number of fallacies associated with causation, the mostfrequently discussed ispost hoc ergo propter hoc, (afterthis, therefore because of this). This fallacy ascribes a causalrelationship between two states or events on the basis of temporalsuccession. For example,

Unemployment decreased in the fourth quarter because the governmenteliminated the gasoline tax in the second quarter.

The decrease in unemployment that took place after the elimination ofthe tax may have been due to other causes; perhaps new industrialmachinery or increased international demand for products. Otherfallacies involve confusing the cause and the effect, and overlookingthe possibility that two events are not directly related to each otherbut are both the effect of a third factor, a common cause. Thesefallacies are perhaps better understood as faults of explanation thanfaults of arguments.

8. The fallacy ofignoratio elenchi, or irrelevantconclusion, is indicative of misdirection in argumentation rather thana weak inference. The claim that Calgary is the fastest growing cityin Canada, for example, is not defeated by a sound argument showingthat it is not the biggest city in Canada. A variation ofignoratio elenchi, known under the name of the straw manfallacy, occurs when an opponent’s point of view is distorted inorder to make it easier to refute. For example, in opposition to aproponent’s view that (a) industrialization is the cause ofglobal warming, an opponent might substitute the proposition that (b)all ills that beset mankind are due to industrialization and then,having easily shown that (b) is false, leave the impression that (a),too, is false. Two things went wrong: the proponent does not hold (b),and even if she did, the falsity of (b) does not imply the falsity of(a).

There are a number of common fallacies that begin with the Latinprefix ‘ad’ (‘to’ or‘toward’) and the most common of these will be describednext.

9. Thead verecundiam fallacy concerns appeals to authorityor expertise. Fundamentally, the fallacy involves accepting asevidence for a proposition the pronouncement of someone who is takento be an authority but is either not really an authority or a relevantauthority. This can happen when non-experts parade as experts infields in which they have no special competence—when, forexample, celebrities endorse commercial products or social movements.Similarly, when there is controversy, and authorities are divided, itis an error to base one’s view on the authority of just some ofthem. (See also 2.4 below.)

10. The fallacyad populum is similar to theadverecundiam, the difference being that the source appealed to ispopular opinion, or common knowledge, rather than a specifiedauthority. So, for example:

These days everyone (except you) has a car and knows how to drive;
So, you too should have a car and know how to drive.

Often in arguments like this the premises aren’t true, but evenif they are generally true they may provide only scant support fortheir conclusions because that something is widely practised orbelieved is not compelling evidence that it is true or that it shouldbe done. There are few subjects on which the general public can besaid to hold authoritative opinions. Another version of theadpopulum fallacy is known as “playing to the gallery”in which a speaker seeks acceptance for his view by arousing relevantprejudices and emotions in his audience in lieu of presenting it withgood evidence.

11. Thead baculum fallacy is one of the most controversialbecause it is hard to see that it is a fallacy or even that itinvolves bad reasoning.Ad baculum means “appeal to thestick” and is generally taken to involve a threat of injury ofharm to the person addressed. So, for example,

If you don’t join our demonstration against the expansion of thepark, we will evict you from your apartment;
So, you should join our demonstration against the expansion of thepark.

Such threats do give us reasons to act but, unpleasant as theinterlocutor may be, there seems to be no fallacy here. In labourdisputes, and perhaps in international relations, using threats suchas going on strike, or cutting off trade routes, are not normallyconsidered fallacies, even though they do involve intimidation and thethreat of harm. However, if we change to doxastic considerations, thenthe argument that you shouldbelieve that candidate \(X\) isthe one best suited for public office because if you do not believethis you will be evicted from your apartment, certainly is a goodinstance of irrelevant evidence.

12. The fallacyad misericordiam is a companion to theadbaculum fallacy: it occurs not when threats are out of place butwhen appeals for sympathy or pity are mistakenly thought to beevidence. To what extent our sympathy for others should influence ouractions depends on many factors, including circumstances and ourethical views. However, sympathy alone is generally not evidence forbelieving any proposition. Hence,

You should believe that he is not guilty of embezzling thosepaintings; think of how much his family suffered during theDepression.

Ad misericordiam arguments, likead baculumarguments, have their natural home in practical reasoning; it is whenthey are used in theoretical (doxastic) argumentation that thepossibility of fallacy is more likely.

13. Thead hominem fallacy involves bringing negative aspectsof an arguer, or their situation, to bear on the view they areadvancing. There are three commonly recognized versions of thefallacy. The abusivead hominem fallacy involves saying thatsomeone’s view should not be accepted because they have someunfavorable property.

Thompson’s proposal for the wetlands may safely be rejectedbecause last year she was arrested for hunting without a license.

The hunter Thompson, although she broke the law, may nevertheless havea very good plan for the wetlands.

Another, more subtle version of the fallacy is the circumstantialad hominem in which, given the circumstances in which thearguer finds him or herself, it is alleged that their position issupported by self-interest rather than by good evidence. Hence, thescientific studies produced by industrialists to show that the levelsof pollution at their factories are within the law may be undeservedlyrejected because they are thought to be self-serving. Yet it ispossible that the studies are sound: just because what someone says isin their self-interest, does not mean it should be rejected.

The third version of thead hominem fallacy is thetuquoque. It involves not accepting a view or a recommendationbecause the espouser him- or herself does not follow it. Thus, if ourneighbor advises us to exercise regularly and we reject her advice onthe basis that she does not exercise regularly, we commit thetuquoque fallacy: the value of advice is not wholly dependent onthe integrity of the advisor.

We may finish our survey of the core fallacies by considering just twomore.

14. The fallacy offaulty analogy occurs when analogies areused as arguments or explanations and the similarities between the twothings compared are too remote to support the conclusion.

If a child gets a new toy he or she will want to play with it;
So, if a nation gets new weapons, it will want to use them.

In this example (due to Churchill 1986, 349) there is a greatdifference between using (playing with) toys and using (discharging)weapons. The former is done for amusement, the latter is done toinflict harm on others. Playing with toys is a benign activity thatrequires little justification; using weapons against others nations issomething that is usually only done after extensive deliberation andas a last resort. Hence, there is too much of a difference betweenusing toys and using weapons to conclude that a nation, if it acquiresweapons, will want to use them as readily as children will want toplay with their toys.

15. The fallacy of theslippery slope generally takes theform that from a given starting point one can by a series ofincremental inferences arrive at an undesirable conclusion, andbecause of this unwanted result, the initial starting point should berejected. The kinds of inferences involved in the step-by-stepargument can be causal, as in:

You have decided not to go to college;
If you don’t go to college, you won’t get a degree;
If you don’t get a degree, you won’t get a good job;
If you don’t get a good job, you won’t be able to enjoylife;
But you should be able to enjoy life;
So, you should go to college.

The weakness in this argument, the reason why it is a fallacy, lies inthe second and third causal claims. The series of small steps thatlead from an acceptable starting point to an unacceptable conclusionmay also depend on vague terms rather than causal relations. Lack ofclear boundaries is what enables the puzzling slippery slope argumentsknown as “the beard” and “the heap.” In theformer, a person with a full beard eventually becomes beardless ashairs of the beard are removed one-by-one; but because the term‘beard’ is vague it is unclear at which intermediate pointwe are to say that the man is now beardless. Hence, at each step inthe argument until the final hair-plucking, we should continue toconclude that the man is bearded. In the second case, because‘heap’ is vague, it is unclear at what point pilingscattered stones together makes them a heap of stones: if it is not aheap to begin with, adding one more stone will not make it a heap,etc. In both these cases apparently good reasoning leads to a falseconclusion.

Many other fallacies have been named and discussed (see, e.g.,Nickerson 2021, ch. 6), some of them quite different from the onesmentioned above, others interesting and novel variations of the above.Some of these will be mentioned in the review of historical andcontemporary sources that follows.

2. History of Fallacy Theory

2.1 Aristotle

The history of the study of fallacies begins with Aristotle’swork,On Sophistical Refutations. It is among his earlierwritings and the work appears to be a continuation of theTopics, his treatise on dialectical argumentation. Althoughhis most extensive and theoretically detailed discussion of fallaciesis in theSophistical Refutations, Aristotle also discussesfallacies in thePrior Analytics andOn Rhetoric.Here we will concentrate on summarizing the account given in theSophistical Refutations. In that work, four things are worthnoting: (a) the different conceptions of fallacy; (b) the basicconcepts used to explain fallacies; (c) Aristotle’s explanationof why fallacies can be deceptive; and (d) his enumeration andclassification of fallacies.

2.1.1 Definitions

At the beginning ofTopics (I, i), Aristotle distinguishesseveral kinds of deductions (syllogisms). They are distinguished firston the basis of the status of their premises. (1) Those that beginfrom true and primary premises, or are owed to such, aredemonstrations. (2) Those which have dialecticalpremises—propositions acceptable to most people, or to thewise—are dialectical deductions. (3) Deductions that start frompremises which only appear to be dialectical, are fallaciousdeductions because of their starting points, as are (4) those“deductions” that do have dialectical premises but do notreally necessitate their conclusions. Other fallacies mentioned andassociated with demonstrations are (5) those which only appear tostart from what is true and primary (Top., I, i 101a5). Whatthis classification leaves out are (6) the arguments that do startfrom true and primary premises but then fail to necessitate theirconclusions; two of these, begging the question and non-cause arediscussed inPrior Analytics (II, 16, 17). It is the“fallacious deductions” characterized in (4), however,that come closest to the focus of theSophisticalRefutations. Nevertheless, in many of the examples given whatstands out is that the premises are given as answers in dialogue andare to be maintained by the answerer, not necessarily that they aredialectical in the sense of being common opinions. This variation ondialectical deductions Aristotle calls examination arguments(SR 2 165b4).

2.1.2 The basic concepts

There are three closely related concepts needed to understandsophistical refutations. By adeduction (a syllogism^[3]) Aristotle meant an argument which satisfies three conditions: it“is based on certain statements made in such a way asnecessarily to cause the assertion of things other than thosestatements and as a result of those statements” (SR 1165a1–2). Thus an argument may fail to be a syllogism in threedifferent ways. The premises may fail to necessitate the conclusion,the conclusion may be the same as one of the premises, and theconclusion may not be caused by (grounded in) the premises. Theconcept of aproof underlyingSophisticalRefutations is similar to what is demanded of demonstrativeknowledge inPosterior Analytics (I ii 71b20), viz., that thepremises must be “true, primary, immediate, better known than,prior to, and causative of the conclusion,” except that thefirst three conditions do not apply to deductions in which thepremises are obtained through questioning. Arefutation,Aristotle says, is “a proof of the contradictory”(SR 6, 168a37)—a proof of the proposition which is thecontradictory of the thesis maintained by the answerer. In a contextof someone,S, maintaining a thesis,T, adialectical refutation will consist in asking questions ofS,and then takingS’s answers and using them as thepremises of a proof via a deduction ofnot-T: this will be arefutation ofT relative to the answerer (SR 8170a13). The concept of contradiction can be found inCategories: it is those contraries which are related suchthat “one opposite needs must be true, while the other mustalways be false” (13b2–3). A refutation will besophistical if either the proof is only an apparent proof or thecontradiction is only an apparent contradiction. Either way, accordingto Aristotle, there is a fallacy. Hence, the opening of his treatise:“Let us now treat of sophistical refutations, that is, argumentswhich appear to be refutations but are really fallacies and notrefutations” (SR 1 164a20).

2.1.3 The appearance condition

Aristotle observed that “reasoning and refutation are sometimesreal and sometimes not, but appear to be real owing to men’sinexperience; for the inexperienced are like those who view thingsfrom a distance” (SR, 1 164b25). The ideas here arefirst that there are arguments that appear to be better than theyreally are; and second that people inexperienced in arguments maymistake the appearance for the reality and thus be taken in by a badargument or refutation. Apparent refutations are primarily explainedin terms of apparent deductions: thus, with one exception,Aristotle’s fallacies are in the main a catalogue of baddeductions that appear to be good deductions. The exception isignoratio elenchi in which, in one of its guises, thededuction contains no fallacy but the conclusion proved only appearsto contradict the answerer’s thesis.

Aristotle devotes considerable space to explaining how the appearancecondition may arise. At the outset he mentions the argument that turnsupon names (SR 1 165a6), saying that it is the most prolificand usual explanation: because there are more things than names, somenames will have to denote more than one thing, thereby creating thepossibility of ambiguous terms and expressions. That the ambiguous useof a term goes unnoticed allows the illusion that an argument is areal deduction. The explanation of how the false appearance can ariseis in the similarity of words or expressions with different meanings,and the smallness of differences in meaning between some expressions(SR 7 169a23–169b17).

2.1.4 List and classification

Aristotle discusses thirteen ways in which refutations can besophistical and divides them into two groups. The first group,introduced in Chapter 4 ofOn Sophistical Refutations,includes those Aristotle considers dependent on language (indictione), and the second group, introduced in Chapter 5,includes those characterized as not being dependent on language(extra dictionem). Chapter 6 reviews all the fallacies fromthe view point of failed refutations, and Chapter 7 explains how theappearance of correctness is made possible for each fallacy. Chapters19–30 advise answerers on how to avoid being taken in bysophistical refutations.

The fallacies dependent on language are equivocation, amphiboly,combination of words, division of words, accent and form ofexpression. Of these the first two have survived pretty much asAristotle thought of them. Equivocation results from the exploitationof a term’s ambiguity and amphiboly comes about throughindefinite grammatical structure. The one has to do with semanticalambiguity, the other with syntactical ambiguity. However, the way thatAristotle thought of the combination and division fallacies differssignificantly from modern treatments of composition and division.Aristotle’s fallacies are the combinations and divisions ofwords which alter meanings, e.g., “walk while sitting” vs.“walk-while-sitting,” (i.e., to have the ability to walkwhile seated vs. being able to walk and sit at the same time). Fordivision, Aristotle gives the example of the number 5: it is 2 and 3.But 2 is even and 3 is odd, so 5 is even and odd. Double meaning isalso possible with those words whose meanings depend on how they arepronounced, this is the fallacy of accent, but there were no accentsin written Greek in Aristotle’s day; accordingly, this fallacywould be more likely in written work. What Aristotle had in mind issomething similar to the double meanings that can be given to‘unionized’ and ‘invalid’ depending on howthey are pronounced. Finally, the fallacy that Aristotle calls form ofexpression exploits the kind of ambiguity made possible by what wehave come to call category mistakes, in this case, fitting words tothe wrong categories. Aristotle’s example is the word‘flourishing’ which may appear to be a verb because of its‘ing’ ending (as in ‘cutting’ or‘running’) and so belongs to the category of actions,whereas it really belongs in the category of quality. Categoryconfusion was, for Aristotle, the key cause of metaphysicalmistakes.

There are seven kinds of sophistical refutation that can occur in thecategory of refutations not dependent on language: accident,secundum quid, consequent, non-cause, begging the question,ignoratio elenchi and many questions.

The fallacy of accident is the most elusive of the fallacies onAristotle’s list. It turns on his distinction between two kindsof predication, unique properties and accidents (Top. I 5).The fallacy is defined as occurring when “it is claimed thatsome attribute belongs similarly to the thing and to itsaccident” (SR 5 166b28). What belongs to a thing areits unique properties which are counterpredicable (Smith 1997, 60),i.e., if \(A\) is an attribute of \(B\), \(B\) is an attribute of\(A\). However, attributes that are accidents are notcounterpredicates and to treat them as such is false reasoning, andcan lead to paradoxical results; for example, if it is a property oftriangles that they are equal to two right angles, and a triangle isaccidentally a first principle, it does not follow that all firstprinciples have two right angles (see Schreiber 2001, ch. 7).

Aristotle considers the fallacy of consequent to be a special case ofthe fallacy of accident, observing that consequence is notconvertible, i.e., “if \(A\) is, \(B\) necessarily is, men alsofancy that, if \(B\) is, \(A\) necessarily is” (SR 5169b3). One of Aristotle’s examples is that it does not followthat “a man who is hot must be in a fever because a man who isin a fever is hot” (SR 5 169b19). This fallacy issometimes claimed as being an early statement of the formal fallacy ofaffirming the consequent.

The fallacy ofsecundum quid comes about from failing toappreciate the distinction between using words absolutely and usingthem with qualification. Spruce trees, for example, are green withrespect to their foliage (they are ‘green’ withqualification); it would be a mistake to infer that they are greenabsolutely because they have brown trunks and branches. It is becausethe difference between using words absolutely and with qualificationcan be minute that this fallacy is possible, thinks Aristotle.

Begging the question is explained as asking for the answer (theproposition) which one is supposed to prove, in order to avoid havingto make a proof of it. Some subtlety is needed to bring about thisfallacy such as a clever use of synonymy or an intermixing ofparticular and universal propositions (Top. VIII, 13). If thefallacy succeeds the result is that there will be no deduction:begging the question and non-cause are directly prohibited by thesecond and third conditions respectively of being a deduction(SR 6 168b23).

The fallacy of non-cause occurs in contexts ofad impossibilearguments when one of the assumed premises is superfluous for deducingthe conclusion. The superfluous premise will then not be a factor indeducing the conclusion and it will be a mistake to infer that it isfalse since it is a non-cause of the impossibility. This is not thesame fallacy mentioned by Aristotle in theRhetoric (II 24)which is more akin to a fallacy of empirical causation and is bettercalledfalse cause (see Woods and Hansen 2001).

Aristotle’s fallacy of many questions occurs when two questionsare asked as if they are one proposition. A proposition is “asingle predication about a single subject” (SR 6169a8). Thus with a single answer to two questions one has twopremises for a refutation , and one of them may turn out to be idle,thus invalidating the deduction (it becomes a non-cause fallacy). Alsopossible is that extra-linguistic part-whole mistakes may happen when,for example, given that something is partly good and partly not-good,the double question is asked whether it is all good or all not-good?Either answer will lead to a contradiction (see Schreiber 2000,156–59). Despite its name, this fallacy consists in the ensuingdeduction, not in the question which merely triggers the fallacy.

On one interpretationignoratio elenchi is considered to beAristotle’s thirteenth fallacy, in which an otherwise successfuldeduction fails to end with the required contradictory of theanswerer’s thesis. Seen this way,ignoratio elenchi isunlike all the other fallacies in that it is not an argument thatfails to meet one of the criteria of a good deduction, but a genuinededuction that turns out to be irrelevant to the point at issue. Onanother reading,ignoratio elenchi is not a separate fallacybut an alternative to the language dependent / language independentway of classifying the other twelve fallacies: they all fail to meet,in one way or another, the requirements of a sound refutation.

[A] refutation is a contradiction of one and the same predicate, notof a name but of a thing, and not of a synonymous name but of anidentical name, based on the given premises and following necessarilyfrom them (the original point at issue not being included) in the samerespect, manner and time. (SR 5 167a23–27)

Each of the other twelve fallacies is analysed as failing to meet oneof the conditions in this definition of refutation (SR 6).Aristotle seems to favour this second reading, but it leaves theproblem of explaining how refutations that miss their mark can seemlike successful refutations. A possible explanation is that a failureto contradict a given thesis can be made explicit by adding thenegation of the thesis as a last step of the deduction, therebyinsuring the contradiction of the thesis, but only at the cost (by thelast step) of introducing one of the other twelve fallacies in thededuction.

2.1.5 Different interpretations

I have given only the briefest possible explanation ofAristotle’s fallacies. To really understand them a much longerengagement with the original text and the secondary sources isnecessary. The second chapter of Hamblin’s (1970) book is auseful introduction to theSophistical Refutations, and adefence of the dialectical nature of the fallacies. Hamblin thinksthat a dialectical framework is indispensable for an understanding ofAristotle’s fallacies and that part of the poverty ofcontemporary accounts of fallacies is due to a failure to understandtheir assumed dialectical setting. This approach to the fallacies iscontinued in contemporary research by some argumentation theorists,most notably Douglas Walton (1995) who also follows Aristotle inrecognizing a number of different kinds of dialogues in whichargumentation can occur; Frans van Eemeren and Rob Grootendorst (2004)who combine dialectical and pragmatic insights with an ideal model ofa critical discussion; and Jaakko Hintikka who analyses theAristotelian fallacies as mistakes in question-dialogues (Hintikka1987; Bachman 1995.) According to Hintikka (1997) it is an outrightmistake to think of Aristotle’s fallacies primarily as mistakeninferences, either deductive or inductive. A non-dialogue orientedinterpretation of Aristotle fallacies is found in Woods and Hansen(1997 and 2001) who argue that the fallacies (apparent deductions) arebasic to apparent refutations, and that Aristotle’s interest inthe fallacies extended beyond dialectical contests, as is shown by hisinterest in them in thePrior Analytics and theRhetoric (II 24). What gives unity to Aristotle’sdifferent fallacies on this view is not a dialogue structure butrather their dependence on the concepts of deduction and proof. Themost thorough recent study of these questions is in Schreiber (2003),who emphasizes Aristotle’s concern with resolving (exposing)fallacies and argues that it is Aristotelian epistemology andmetaphysics that is needed for a full understanding of the fallaciesin theSophistical Refutations.

2.2 Bacon

Francis Bacon deserves a brief mention in the history of fallacytheory, not because he made any direct contribution to our knowledgeof the fallacies but because of his attention to prejudice and bias inscientific investigation, and the effect they could have on ourbeliefs. He spoke of false idols (1620, aphorisms 40–44) ashaving the same relation to the interpretation of nature thatfallacies have to logic. The idol of the tribe is human nature whichdistorts our view of the natural world (it is a false mirror). Theidol of the cave is the peculiarity of each individual man, ourdifferent abilities and education that affect how we interpret nature.The idols of the theatre are the acquired false philosophies, systemsand methods, both new and ancient, that rule men’s minds. Thesethree idols all fall into the category of explanations of why we maymisperceive the world. A fourth of Bacon’s idols, the idol ofthe market place, is the one that comes closest to the Aristoteliantradition as it points to language as the source of our mistakenideas: “words plainly force and overrule the understanding, andthrow all into confusion, and lead men away into numberless emptycontroversies and idle fancies” (1620, aphorism 43). AlthoughBacon identifies no particular fallacies in Aristotle’s sense,he opens the door to the possibility that there may be falseassumptions associated with the investigation of the natural world.The view ofThe New Organon is that just as logic is the curefor fallacies, so will the true method of induction be a cure for thefalse idols.

2.3 Arnauld and Nicole

Antoine Arnauld and Pierre Nicole were the authors ofLogic, orthe Art of Thinking (1662), commonly known as the Port-RoyalLogic. According to Benson Mates (1965, 214) it “is anoutstanding early example of the ‘how to think straight’genre.” The work includes chapters on sophisms, with thejustification that “examples of mistakes to be avoided are oftenmore striking than the examples to be imitated” (Bk. III, xix).The Port-Royal Logic does not continue Aristotle’s distinctionbetween fallacies that are dependent on language and those that arenot; instead there is a division between sophisms associated withscientific subjects (ibid.)—these are nearly all from theSophistical Refutations—and those committed in everydaylife and ordinary discourse (Bk III, xx). The division is notexclusive, with some of the sophisms fitting both classes.

The Port-Royal Logic includes eight of Aristotle’s originalthirteen fallacies, several of them modified to fit the bent tonatural philosophy rather than dialectical argumentation. Severalkinds of causal errors are considered under the broad heading,noncausa pro causa and they are illustrated with reference toscientific explanations that have assigned false causes for empiricalphenomena. Also identified as a common fallacy of the human mind ispost hoc, ergo propter hoc: “This happened following acertain thing, hence that thing must be its cause” (Bk. III, xix3). Begging the questions is included and illustrated, interestingly,with examples drawn from Aristotelian science. Two new sophisms areincluded: one is imperfect enumeration, the error of overlooking analternative, the other is a faulty (incomplete) induction, what wemight call hasty generalization. Although the discussions here arebrief, they mark the entry of inductive fallacies into the pool ofpresent day recognized fallacies.Ignoratio elenchi retainsits dialogical setting but is extended beyond the mere failure tocontradict a thesis, “to attribut[ing] to our adversariessomething remote from their views to gain an advantage over them, orto impute to them consequences we imagine can be drawn from theirdoctrines, although they disavow and deny them” (Bk. III, xix1). The other Aristotelian fallacies included are accident,combination and division,secundum quid and ambiguity.

The sophisms of everyday life and ordinary discourse are eight innumber and two of them, the sophisms of authority and manner, shouldbe noticed. In these sophisms, external marks of speakers contributeto the persuasiveness of their arguments. Although authority is not tobe doubted in church doctrines, in matters that God has left to thediscernment of humans we can be led away from the truth by being toodeferential. Here we find one of the earliest statements of the modernappeal to false authority: people are often persuaded by certainqualities that are irrelevant to the truth of the issue beingdiscussed. Thus there are a number of people who unquestioninglybelieve those who are the oldest and most experienced, even in mattersthat depend neither on age nor experience, but only on mental insight(Bk. III, xx 6). To age and experience Arnauld and Nicole add noblebirth as an unwarranted source of deference in matters intellectual(Bk. III, xx 7), and towards the end of their discussion they add thesophism of manner, cautioning that “grace, fluency, seriousness,moderation and gentleness” is not necessarily a mark of truth(Bk. III, xx 8). The authors seem to have the rhetorical flourishes ofroyal courtiers especially in mind.

2.4 Locke

It is John Locke who is credited with intentionally creating a classofad-arguments, and inadvertently giving birth to the classofad-fallacies. InAn Essay Concerning HumanUnderstanding (1690), he identified three kinds of arguments, thead verecundiam,ad ignorantiam, andadhominem arguments, each of which he contrasted withadjudicium arguments which are arguments based on “thefoundations of knowledge and probability” and are reliableroutes to truth and knowledge. Locke did not speak ofad-arguments as fallacies—that was left to others to dolater—but rather as kinds of arguments “that men, in theirreasoning with others, do ordinarily make use of to prevail on theirassent; or at least so to awe them as to silence theiropposition.” (Bk IV, xvii, 19–22).

Two of thead arguments have developed beyond how Lockeoriginally conceived them. His characterization of theadverecundiam is considered thelocus classicus ofappeal-to-authority arguments. When it is a fallacy it is either onthe ground that authorities (experts) are fallible or for the reasonthat appealing to authority is an abandonment of an individual’sepistemic responsibility. It seems unlikely, however, that Lockethought we should never rely on the expertise and superior knowledgeof others when engaged in knowledge-gathering and argumentation. Thisleads us to consider what kind of authority Locke might have had inmind. In addition to epistemic and legal (command) authority there isalso what might be called social authority, demanding respect anddeference from others due to one’s higher social standing,something much more a part of seventeenth-century society than it is apart of ours. The language that Locke used in connection with thead verecundiam, words like ‘eminency’,‘dignity’, ‘breach of modesty’, and‘having too much pride’ suggests that what he had in mindwas the kind of authority that demands respect for the social standingof sources rather than for their expertise; hence, by this kind ofauthority a person could be led to accept a conclusion because oftheir modesty or shame, more so than for the value of the argument(see Goodwin 1998). Hence, we understand Locke better when wetranslatead verecundiam literally, as “appeal tomodesty.”

The argumentumad hominem, as Locke defined it, hassubsequently developed into three different fallacies. His originaldescription was that it was a way “to press a man withconsequences drawn from his own principles or concessions.” Thatis, to argue that an opponent’s view is inconsistent, logicallyor pragmatically, with other things he has said or to which he iscommitted. Locke’s observation was that such arguments do notadvance us towards truth, but that they can serve to promote agreementor stall disagreement. To argue that way is not a fallacy but anacceptable mode of argumentation. Henry Johnstone (1952) thought itcaptured the essential character of philosophical argumentation. Themodern descendants of the Lockeanad hominem are the abusivead hominem which is an argument to the effect that a positionshould not be accepted because of some telling negative property ofits espouser; the circumstantialad hominem, an argument tothe effect that someone’s position should be rejected becausecircumstances suggest that their view is the result of self-interestedbias; and finally, thetu quoque ad hominem argument whichattempts to deflect a criticism by pointing out that it appliesequally to the accuser. Recent scholarship suggests that thesepost-Lockean kinds ofad hominem arguments are sometimes usedfairly, and sometimes fallaciously; but none of them is what Lockedescribed as theargumentum ad hominem.

Ad ignorantiam translates as “appeal toignorance.” Locke’s characterization of this kind ofargument is that it demands “the adversary to admit what theyallege as a proof, or to assign a better.” The ignorance inquestion is comparative, it is not that the opponent has no evidence,it is that s/he has no better evidence. However, the inability of anopponent to produce a better argument is not sufficient reason tothink the proponent’s argument must be accepted. Modern versionsof this kind of argument take it as a fallacy to infer a propositionto be true because there is no evidence against it (see Krabbe,1995).

The introduction and discussion of thead-arguments appearsalmost as an afterthought in Locke’sEssay. It is foundat the end of the chapter, “Of Reason,” in which Lockedevotes considerable effort to criticizing syllogistic logic.Reasoning by syllogisms, he maintained, was neither necessary noruseful for knowledge. Locke clearly thought that the threead-arguments were inferior toad judicium arguments,but he never used the term ‘fallacy’ in connection withthem, although he did use it in connection with errors of syllogisticreasoning.

Was Locke the first to discuss these kinds of arguments? Hamblin(1970, 161–62) and Nuchelmans (1993) trace the idea ofadhominem arguments back to Aristotle, and Locke’s remarkthat the nameargumentum ad hominem was already known hasbeen investigated by Finocchiaro (1974) who finds the term and theargument kind in Galileo’s writings more than a half-centurybefore theEssay Concerning Human Understanding. And Arnauldand Nicole’s discussion of the sophism of authority, that“people speak the truth because they are of noble birth orwealthy or in high office,” which seems to be part ofLocke’sad verecundiam, was most likely known to him.Subsequently moread-arguments were added to the four thatLocke identified (see Watts, and Copi, below).

2.5 Watts

Isaac Watts in hisLogick; or, The Right Use of Reason(1724), furthered thead-argument tradition by adding threemore arguments:argumentum ad fidem (appeal to faith),argumentum ad passiones (appeal to passion), andargumentum ad populum (a public appeal to passions). LikeLocke, Watts does not consider these arguments as fallacies but askinds of arguments. However, theLogick does considersophisms and introduces “false cause” as an alternativename fornon causa pro causa which here, as in the Port-RoyalLogic, is understood as a fallacy associated with empirical causation.According to Watts it occurs whenever anyone assigns “thereasons of natural appearances, without sufficient experiments toprove them” (1796, Pt. III, 3 i 4). Another sophism included byWatts is imperfect enumeration or false induction, the mistake ofgeneralizing on insufficient evidence. Also, the term ‘strawmanfallacy’ may have its origins in Watts’s discussion ofignoratio elenchi: after having dressed up the opinions andsentiments of their adversaries as they please to make “imagesof straw”, disputers “triumph over their adversary asthough they had utterly confuted his opinions” (1796, Pt. III 3i 1).

2.6 Bentham

Jeremy Bentham’sHandbook of Political Fallacies (1824)was written in the years leading up to the first Reform Bill (1832).His interest was in political argumentation, particularly in exposingthe different means used by parliamentarians and law makers to defeator delay reform legislation. Hence, it was not philosophy or sciencethat interested him, but political debate. Fallacies he took to bearguments or topics that would through the use of deception produceerroneous beliefs in people (1824, 3). These tactics he (or hiseditor) divided into four classes: fallacies of authority, danger,delay and confusion. Bentham was aware of the developingad-fallacies tradition since each of the thirty or sofallacies he described is also labelled as belonging either to thekindad verecundiam (appeal to shame or modesty),adodium (appeal to hate or contempt),ad metum (appeal tofear or threats),ad quietem (appeal to rest or inaction),ad judicium, andad socordiam (appeal topostponement or delay). Most of Bentham’s fallacies have notbecome staples of fallacy theory but many of them show interestinginsights into the motives and techniques of debaters (see e.g.,Rudanko’s (2021) analyses of thead socordiam).

Bentham’sHandbook has not taken a central place in thehistory of fallacy studies (Hamblin 1970, 165–69); nevertheless,it is historically interesting in several respects. It discussesauthority at length, identifying four conditions for reliable appealsto authority and maintaining that the failure of any one of themcancels the strength of the appeal. Fallacies of authority inpolitical debate occur when authority “is employed in the placeof such relevant arguments as might have been brought forward”(1824, 25). Bentham’s fear is that debaters will resort to“the authority” of traditional beliefs and principlesinstead of considering the advantages of the reform measures underdiscussion.

Under the heading “fallacies of danger” Bentham named anumber of what he called vituperative fallacies—imputations ofbad character, bad motive, inconsistency, and suspiciousconnections—which have as their common characteristic,“the endeavour to draw aside attention from themeasureto theman, in such a way as to cause the latter’sbadness to be imputed to the measure he supports, or his goodness tohis opposition” (1824, 83). This characterization fits well withthe way we have come to think of thead hominem fallacy as aview disparaged by putting forth a negative characterization of itssupporter or his circumstances.

Bentham places the fallacies in the immediate context of debate,identifying ways in which arguers frustrate the eventual resolution ofdisagreements by using insinuations of danger, delaying tactics,appeals to questionable authorities and, generally, confusing issues.Modern argumentation theorists who hold that any impediment to thesuccessful completion of dialogical discussions is a fallacy, may findthat their most immediate precursor was Bentham (see Grootendorst1997).

2.7 Whately

Book III of Richard Whately’sElements of Logic (1826)is devoted to giving an account of fallacies based on “logicalprinciples,”. Whately was instrumental in the revival ofinterest in logic at the beginning of the nineteenth century and,being committed to deductivism, he maintained that only validdeductive inferences counted as reasoning. Thus, he took every fallacyto belong to either the class of deductive failures (logicalfallacies) or the class of non-logical failures (materialfallacies).

By ‘fallacy’ Whately meant “any unsound mode ofarguing, which appears to demand our conviction, and to be decisive ofthe question at hand, when in fairness it is not”’ (Bk.III, intro.). The logical fallacies divide into the purely logical andthe semi-logical fallacies. The purely logical fallacies are plainviolations of syllogistic rules like undistributed middle and illicitprocess. The semi-logical fallacies mostly trade on ambiguous middleterms and are therefore also logical fallacies, but their detectionrequires extra-logical knowledge including that of the senses of terms^[4] and knowledge of the subject matter (Bk. III, §2); they include,among others, the fallacies of ambiguity, and division andcomposition. The non-logical, material fallacies are also divided intotwo classes: fallacies with premises ‘unduly assumed,’ andfallacies of irrelevant conclusions. Begging the question fits underthe heading of a non-logical, material fallacy in which a premise hasbeen unduly assumed, andignoratio elenchi is a non-logical,material fallacy in which an irrelevant conclusion has been reached.Thead-arguments are all placed under the last division asvariants ofignoratio elenchi, but they are said to befallacies only when they are used unfairly. Whately’s version ofthead hominem argument resembles Locke’s in that it isanex concessis kind of argument: one that depends on theconcessions of the person with whom one is arguing. From theconcessions, one might prove that one’s opponent is‘committed top,’ but an attempt to make it seemas if this constitutes a proof of the absolute (non-relative)proposition ‘p’ would be a fallacy. This kind ofad hominem fallacy can be seen as falling under the broaderignoratio elenchi category because what is proved is not whatis needed.

The creation of the category of non-logical fallacies was not really abreak with Aristotle as much as it was a break with what had becomethe Aristotelian tradition. Aristotle thought that some fallacies weredue to unacceptable premises although these are not elaborated inSophistical Refutations (see section 2.1.1 above).Whately’s creation of the category of non-logical fallaciessolved the problem of what to do with begging the question which isnot an invalid form of argument, and it also created a place infallacy taxonomy for thead-fallacies.

2.8 Mill

John Stuart Mill’s contribution to the study of fallacies isfound in Book V of his comprehensiveA System of Logic,Ratiocinative and Inductive, first published in 1843. It standsout most strikingly for placing the study of fallacies within hisframework of inductive reasoning, a direct rejection ofWhately’s deductivist approach to reasoning and fallacies. Millheld that only inductive reasoning counts as inferring and accordinglyhe introduces new categories as well as a new classification schemefor fallacies.

Mill drew a division between the moral and the intellectual causes offallacies. The former are aspects of human nature such as biases andindifference to truth which incline us to make intellectual mistakes.These dispositions are not themselves fallacies. It is theintellectual errors, the actual taking of insufficient evidence assufficient, that are fallacious. The various ways in which this canhappen are what Mill took as the basis for classifying fallacies.“A catalogue of the varieties of evidence which are not realevidence,” he wrote, “is an enumeration offallacies” (1891, Bk.V iii §1).

Mill divided the broad category of argument fallacies into two groups:those in which the evidence is distinctly conceived and those in whichit is indistinctly conceived. Fallacies falling under evidenceindistinctly conceived (Bk. V, vii) were further described asfallacies of confusion. These result from an indistinct conception ofthe evidence leading to a mistaking of its significance and thereby toan unsupported conclusion. Some of the traditional Aristotelianfallacies such as ambiguity, composition and division,petitioprincipii, andignoratio elenchi, are placed in thiscategory. Although Mill followed Whately closely in his exposition ofthe fallacies of confusion, he does not mention anyad-arguments in connection withignoratioelenchi.

As for the category of fallacies of evidence distinctly conceived, ittoo is divided. The two sub-classes are fallacies of ratiocination(deduction) and fallacies of induction. The deductive fallacies (Bk.V,vi) are those that explicitly break a rule of the syllogism, such asthe three-term rule. But also included are the conversion of universalaffirmatives and particular negatives (“All PS” does notfollow from “All SP,” and “Some P not S” doesnot follow from “Some S not P”). Also included in thiscategory is thesecundum quid fallacy.

The other sub-class of fallacies distinctly conceived bring out whatis distinctive about Mill’s work on the fallacies: that it isthe first extensive attempt to deal with fallacies of induction. Hedivided inductive fallacies into two further groups: fallacies ofobservation (V, iv) and fallacies of generalization (Bk. V, v).Fallacies of observation can occur either negatively or positively.Their negative occurrence consists in non-observation in which one hasoverlooked negatively relevant evidence. This is similar to what thePort-Royal Logic considered a faulty enumeration, and one ofMill’s examples is the continued faith that farmers put in theweather forecasts found in almanacs despite their long history offalse predictions. Observation fallacies occur positively when themistake is based on something that is seen wrongly, i.e., taken to besomething that it is not. Such mal-observations occur when we mistakeour inferences for facts, as in our inference that the sun rises andsets (Bk. V, iv, 5).

Fallacies of generalization, the other branch of inductive fallacies,result from mistakes in the inductive process which can happen inseveral ways. As one example, Mill pointed to making generalizationsabout what lies beyond our experience: we cannot infer that the lawsthat operate in remote parts of the universe are the same as those inour solar system (Bk. V, v, 2). Another example is mistaking empiricallaws stating regularities for causal laws—his example wasbecause women as a class have not hitherto equalled men as a class,they will never be able to do so (Bk. V, v, 4). Also placed in thecategory of fallacies of generalization ispost hoc ergo propterhoc, which tends to single out a single cause when there are inreality many contributing causes (Bk. V, v, 5). Analogical argumentsare identified as a false basis for generalizations; they are“at best only admissible as an inconclusive presumption, wherereal proof is unattainable” (Bk. V, v, 6).

Mill also included what he calls fallacies of inspection, orapriori fallacies (Bk. V, iii) in his survey of fallacies. Theseconsist of non-inferentially held beliefs, so they fit the beliefconception of fallacies rather than the argument conception. AmongMill’s examples ofa priori fallacies are metaphysicalassumptions such as that distinctions of language correspond todistinctions in nature, and that objects cannot affect each other at adistance. Even the belief in souls or ghosts is considered anapriori fallacy. Such beliefs will not withstand scrutiny, thoughtMill, by the inductive method strictly applied.

A System of Logic is the most extensive work on fallaciessince Aristotle’sSophistical Refutations. Mill’sexamples are taken from a wide range of examples in science, politics,economics, religion and philosophy. His classificatory scheme isoriginal and comprehensive. Frederick Rosen (2006) argues thatMill’s pre-occupation with the detection and prevention offallacies is part of what motivates the celebrated second chapter ofOn Liberty. Despite these considerations, theLogicis not much referenced by fallacy theorists.

2.9 Sidgwick

In a series of articles and books beginning in 1878 and continuingwell into the twentieth century, Alfred Sidgwick wrote repeatedlyabout fallacies. Unlike Whately and Mill who thought that searchingfor fallacies was a supplement to their logical methods (deduction andinduction, respectively), Sidgwick wanted to put argument evaluationby fallacies at the centre of logic. In his view, the negative methodof evaluating arguments by searching them for fallacies is a morepractical and efficient way of judging arguments in actual life thanthe positive method of trying to match arguments with the positivestandards of formal logic. His earliest proposal (1878) was to passarguments through a sieve, or filter, which would eliminate argumentsif they had the marks of any of the fallacies. Sidgwick placed thecategory of fallacies of confusion (those due to ambiguity orvagueness), includingignoratio elenchi, at the top of thesieve. At the next level down ispetitio principii andarguments from occult causes, and below that fallacies ofratiocination (deductive, syllogistic fallacies) and inductivereasoning. An argument that succeeds in passing all the way throughthe sieve should be considered logically good. He thought mostfallacies would be revealed at the top level as fallacies ofconfusion.

Sidgwick’s contribution is not to the definition of fallacies,nor to the identification of new fallacies, but rather to hispromotion of the idea, worked out in some detail inFallacies: Aview of logic from the practical side (1884), that a systematicsearch for fallacy mistakes could be a comprehensive and practicalmethod of evaluating arguments found in daily life. He was one of thefirst to argue that the new mathematical interpretations of logicbeing advanced in the second-half of the nineteenth century could notdo justice to natural language arguments, and he was also an advocatefor reform in how logic should be taught so as to make it practicallyvaluable to students. Although Sidgwick’s work is little knowntoday, it is fair to say that he anticipated many of the concerns thatwould occupy informal logic a hundred years later.

2.10 Copi

Irving Copi’sIntroduction to Logic—aninfluential text book from the mid-twentieth century—defines afallacy as “a form of argument that seems to be correct butwhich proves, upon examination, not to be so.” (1961, 52) Theterm ‘correct’ is sufficiently broad to allow for bothdeductive invalidity, inductive weakness, as well as some other kindsof argument failure. Of the eighteen informal fallacies Copidiscusses, eleven can be traced back to the Aristotelian tradition,and the other seven to the burgeoning post-Lockeanad-fallacytradition.

The first division in Copi’s classification is between formaland informal fallacies. Formal fallacies are invalid inferences which“bear a superficial resemblance” to valid forms ofinference, so these we may think of as deductive fallacies. Theyinclude affirming the consequent, denying the antecedent, the fallacyof four terms, undistributed middle, and illicit major. Informalfallacies are not characterized as resembling formally validarguments; they gain their allure some other way. One division ofinformal fallacies is the fallacies of relevance which are“errors in reasoning into which we may fall because ofcarelessness and inattention to our subject matter” (1961, 53).This large class of fallacies includes accident, converse accident,false cause,petitio principii, complex question,ignoratio elenchi,ad baculum,ad hominemabusive,ad hominem circumstantial,ad ignorantiam,ad misericordiam,ad populum, andadverecundiam. The other division of informal fallacies is calledfallacies of ambiguity and it includes equivocation, amphiboly,accent, composition and division.

It seems that Copi took Whately’s category of semi-logicalfallacies and moved them under a new heading of ‘informalfallacies,’ presumably for the reason that extra-logicalknowledge is needed to uncover their invalidity. This has the resultthat the new wide category of informal fallacies is a mixed bag: someof them are at bottom logical failures (equivocation, composition,ad misericordiam) and some are logically correct butfrustrate proof (begging the question,ignoratio elenchi).^[5] Copi’s classification, unlike Whately’s which sought tomake a distinction on logical grounds, may be seen as based on threeways that fallacies resemble good arguments: formal fallacies haveinvalid forms that resemble valid forms, fallacies of ambiguityresemble good arguments through the ambiguity of terms, and fallaciesof relevance exploit psychological (non-logical) associations. Hence,we may think of Copi’s divisions as between logical, semanticand psychological fallacies.

Copi’s treatment of the fallacies is a fair overview of thetraditional list of fallacies, albeit he did not pretend to do anymore than give an introduction to existing fallacy-lore for beginninglogic students. Hamblin (1970, ch. 1) criticized Copi’s work,along with that of several others, and gave it the pejorative name,“the standard treatment of fallacies.” His criticisms rangtrue with many of his readers, thereby provoking contempt for thetraditional treatment of fallacies as well as stimulating research inwhat we may call the new, or post-Hamblin, era, of fallacy studies.Let us next consider some of these developments.

3. New approaches to fallacies

3.1 Renewed interest

A common complaint since Whately’sElements of Logic isthat our theory and teaching of fallacies are in want ofimprovement—he thought they should be put on a more logicalfooting to overcome the loose and vague treatments others hadproffered.

It is on Logical principles therefore that I propose to discuss thesubject of Fallacies. … the generality of Logical writers haveusually followed so opposite a plan. Whenever they have to treat ofanything that is beyond the mere elements of Logic, they totally layaside all reference to the principles they have been occupied inestablishing and explaining, and have recourse to a loose, vague, andpopular kind of language … [which is] … strangelyincongruous in a professional Logical treatise. (1875, III, intro.)

Charles Hamblin’s 1970 book,Fallacies, revivesWhately’s complaint. We may viewFallacies as thedividing line between traditional approaches to the study of fallaciesand new, contemporary approaches. At the time of its publication itwas the first book-length work devoted to fallacies in modern times.The work opens with a critique of the standard treatment of fallaciesas it was found in mid-twentieth century textbooks; then, insubsequent chapters, it takes a historical turn reviewingAristotle’s approach to fallacies and exploring the tradition itfostered (as in the previous section of this entry). Otherhistorically-oriented chapters include one on the Indian tradition,and one on formal fallacies. Hamblin’s more positivecontributions to fallacy studies are concentrated in the book’slater chapters on the concept of argument, formal dialectics, andequivocation.

What Hamblin meant by “the standard treatment offallacies” was:

The typical or average account as it appears in the typical shortchapter or appendix of the average modern textbook. And what we findin most cases, I think it should be admitted, is as debased, worn-outand dogmatic a treatment as could be imagined—incrediblytradition bound, yet lacking in logic and in historical sense alike,and almost without connection to anything else in modern Logic at all.(1970, 12)

Let us consider what came before Hamblin as the traditional approachto fallacies and what comes after him as new approaches. The newapproaches (since the 1970’s) show a concern to overcomeHamblin’s criticisms, and they also vie with each to produce themost defensible alternative to the traditional approach. One thingthat nearly all the new approaches have in common is that they rejectwhat Hamblin presents as the nearly universally accepted definition of“fallacy” as an argument “thatseems to bevalid butis not so” (1970, 12). Although thisdefinition of fallacy is not nearly as widely accepted as Hamblinintimated (see Hansen 2002), others have taken to calling it“the standard definition of fallacies” and for conveniencewe can refer to it as SDF. SDF has three necessary conditions: afallacy (i) is an argument, (ii) that is invalid, and (iii) appears tobe valid. These can be thought of as the argument condition, theinvalidity condition and the appearance condition. All threeconditions have been brought into question.

3.2 Doubts about fallacies

Maurice Finocchiaro continued Hamblin’s criticism of the moderntextbook treatment of fallacies, observing that they contain very fewexamples of actual fallacies, leading him to doubt the validity of‘fallacy’ as a genuine logical category. Although heallows that errors in reasoning are common in real life, he thinksthat “types of logically incorrectarguments”—fallacies—are probably not common (1981,113). For that reason Finocchiaro prefers to speak offallaciousarguments—by which he means arguments in which theconclusion fails to follow from the premises—rather thanfallacies (1987, 133). He further distances himself from SDFby not considering the appearance condition.

Finocchiaro distinguishes six ways in which arguments can befallacious. (1)Formal fallaciousness is simply the casewhere the conclusion does not follow validly from the premises; thistype of error can be demonstrated by producing a suitable analogouscounter-example in which the premises are true and the conclusion isfalse. (2)Explanatory fallaciousness occurs when a specifiedconclusion follows with no more certainty from the given premises thandoes a rival conclusion; it occurs most often in the context ofproposing explanatory hypotheses. (3)Presuppositionalfallaciousness occurs in those cases where an argument depends ona false presupposition; this kind of fallaciousness is demonstrated bymaking a sound argument showing the presupposition to be false. (4)Positive fallaciousness occurs when the given premises,complemented by other propositions taken as true, are shown to supporta conclusion inconsistent with the given conclusion. (5)Semantical fallaciousness results from the ambiguity ofterms; the conclusion will follow if the sense given to the term inthe premises makes the premises false, but if the other sense isascribed to the term, making the premises true, the conclusion doesnot follow (it becomes an instance of formal fallaciousness). (6)Finally, Finocchiaro singles outpersuasive fallaciousness,in which the conclusion does not follow from the premises because itis the same as one of the premises. As a test of completeness of thissix-fold division of fallaciousness, Finocchiaro (1987) observes thatit is adequate to classify all the kinds of errors which Galileo foundin the arguments of the defenders of the geocentric view of the solarsystem.

Gerald Massey (1981) has voiced a strong objection to fallacy theoryand the teaching of fallacies. He argues that there is no theory ofinvalidity—no systematic way to show that an argument is invalidother than to show that it has true premises and a false conclusion(1981, 164). Hence, there is an asymmetry between proving argumentsvalid and proving them invalid: they are valid if they can be shown tobe an instance of a valid form, but they are not proved invalid byshowing that they are an instance of an invalid form, because bothvalid and invalid arguments instantiate invalid forms. Thus, showingthat a natural language argument is an instance of an invalid formdoes not preclude the possibility that it is also an instance of avalid form, and therefore valid. Since upholders of SDF maintain thatfallacies are invalid arguments, Massey’s asymmetry thesis hasthe consequence that no argument can be convicted of being a fallacyon logical grounds.^[6]

3.3 The informal logic approach to fallacies

The informal logic approach to fallacies is taken in Johnson andBlair’sLogical Self-Defense, a textbook firstpublished in 1977. It was prompted in part by Hamblin’sindictment of the standard treatment and it further develops aninitiative taken by Kahane (1971) to develop university courses thatwere geared to everyday reasoning. Johnson and Blair’s emphasisis on arming students to defend themselves against fallacies ineveryday discourse, and a fundamental innovation is in theirconception of a good argument. In place of a sound argument—adeductively valid argument with true premises—Johnson and Blairposit an alternative ideal of acogent argument, one whosepremises are acceptable, relevant to and sufficient for itsconclusion. Acceptability replaces truth as a premise requirement, andthe validity condition is split in to two different conditions,premise relevance and premise sufficiency. Acceptability is definedrelative to audiences—the ones for whom arguments areintended—but the other basic concepts, relevance andsufficiency, although illustrated by examples, remain as intuitive,undefined concepts (see Tindale, 2007). Premise sufficiency (strength)is akin to probability in that it is a matter of degree but Johnsonand Blair do not pursue giving it numerical expression.

The three criteria of a cogent argument, individually necessary andjointly sufficient, lead to a conception of fallacy as “anyargument that violates one of the criteria of good argument …and is committed frequently in argumentative discourse” (1993,317–18). This shares only one condition with SDF: that a fallacyis an argument. (Deductive) validity is replaced with the broaderconcept sufficiency, and the appearance condition is not included.Johnson (1987) argued that the appearance condition makes theoccurrence of fallacies too subjective since how things appear mayvary from perceiver to perceiver, and it should therefore be replacedby a frequency requirement. To be a fallacy, a mistake must occur withsufficient frequency to be worth our attention.

The adoption of the concept of a cogent argument as an ideal hasseveral consequences. The category of fallacies with problematicpremises (reminiscent of Whately’s “premises undulyassumed”) shows a concern with argument evaluation over andbeyond logical or inference evaluation, drawing the informal logicapproach away from purely logical concerns towards an epistemicconception of fallacies. Having both sufficiency and relevance ascriteria (instead of the single validity criterion) has the benefit ofallowing the making of nuanced judgments about the level of premisesupport: for example, we might say that an argument’s premises,although insufficient, are nevertheless positively relevant to theconclusion. Irrelevant premise fallacies are those with no premisesupport at all, whereas insufficient premise fallacies are those inwhich there is some support, but not enough of it. The informallogicians’ conception of fallacies is meant to be broader andmore suitable to natural language argumentation than would be aconception tied only to deductive invalidity.

Johnson and Blair concern themselves exclusively withinformal fallacies. Many of the familiar Aristotelianfallacies that are part of the standard treatment are missing fromtheir inventory (e.g., accident, composition and division) and theones retained find themselves in new categories: begging the questionand ambiguity are together under the heading of Problematic Premise;appeals to authority and popularity are placed under the heading ofHasty Conclusion fallacies;ad hominem is among the fallaciesthat belong in the third category, Fallacies of Irrelevant Reason.This new list of fallacies has a different bent than many earlierlists, being more geared to deal with arguments in popular, everydaycommunication than philosophical or scientific discourse; this isevident both by the omission of some of the traditional fallacies aswell as by the introduction of new ones, such as dubious assumption,two wrongs, slippery slope, and faulty analogy.

The kinds of mistakes one can make in reasoning are generally thoughtto be beyond enumeration and, hence, it has been maintained that therecan be no complete stock of fallacies that will guard against everykind of mistake. Johnson and Blair’s approach is responsive tothis problem in that it allows the names of the classes of fallacies— ‘unacceptable premise,’ ‘irrelevantreason’ and ‘hasty conclusion’ — to stand forfallacies themselves, fallacies broad-in-scope; i.e., to serve“both as general principles of organization, and as back-ups tofill in any gaps between specific labels belonging within eachgenus” (1993, 52). Hence, any violation of one of the criteriaof a cogent argument can be considered a fallacy.

In addition to this alternative theoretical approach to fallaciesbuilt on the three criteria of a cogent argument—an approachalso taken up by others^[7]—informal logic’s contribution to fallacy studies lies in its attempts toprovide better analyses of fallacies, a programme pursued by a largenumber of researchers, including Govier (1982) on the slippery slope,Wreen (1989) on thead baculum, Walton (1991) on begging thequestion, Brinton (1995) on thead hominem, Freeman (1995) onthe appeal to popularity, Pinto (1995) onpost hoc ergo propterhoc and Finocchiaro (2023) on the fallacy of composition.

3.4 The formal approach to informal fallacies

John Woods also despairs of the standard treatment but he sees in itsomething of importance; namely that the fallacies most often reviewedin introductory level logic textbooks “are a kind of caricatureof their associated improprieties, which lie deeply imbedded in humanpractice” (Woods 1992, 25). The fallacies are then behaviouralsymptoms of kinds of irrationality to which humans are highlysusceptible, and that makes them an important subject for studybecause they say something about human nature. Therefore, the problemwith the standard treatment, according to Woods, is not that it is amisdirected research programme, but rather that it has been poorlycarried out, partly because logicians have failed to appreciate that amulti-logical approach is necessary to understand the variety offallacies. This idea, pursued jointly by Woods and Douglas Walton(1989), is that, for many of the fallacies standard formal logic isinadequate to uncover the unique kind of logical mistakes inquestion—it is too coarse conceptually to reveal the uniquecharacter of many of the fallacies. To get a satisfactory analysis ofeach of the fallacies they must be matched with a fitting logicalsystem, one that has the facility to uncover the particular logicalweakness in question. Inductive logic can be employed for analysis ofhasty generalization andpost hoc ergo propter hoc;relatedness logic is appropriate forignoratio elenchi;plausible reasoning theory for thead verecundiam, anddialectical game theory for begging the question and many questions.Woods (1992, 43) refers to this approach to studying the fallacies asmethodological pluralism. Thus, like the informal logicians, there ishere an interest in getting the analyses of each of the fallaciesright, but the Woods and Walton approach involves embracing formalmethods, not putting them aside.

Woods (2013) has continued his research on fallacies, most recentlyconsidering them in the context of what he calls a naturalized logic(modelled on Quine’s naturalized epistemology). The main pointof this naturalizing move is that a theory of reasoning should takeinto account the abilities and motivations of reasoners. Past work onthe fallacies has identified them as failing to satisfy the rules ofeither deductive or inductive logic, but Woods now wants to considerthe core fallacies in light of what he calls third-way reasoning(comparable to non-monotonic reasoning), an account of the cognitivepractices that closely resemble our common inferential practices. Fromthe perspective of third-way reasoning the “rules”implicit in the fallacies present themselves as heuristic directivesto reasoners rather than as fallacies; hence, it may be that learningfrom feedback (having errors corrected) is less trouble than learningthe rules to avoid fallacies in the first place (Woods 2013, p. 215).Woods illustrates his point by recalling many of the fallacies heoriginally identified in his 1992 paper, and subjecting them to thisrevised model of analysis thereby overturning the view that thesetypes of argument are always to be spurned.

3.5 The epistemic approach to fallacies

SDF may be seen as closely tied to the logical approach tofallacies—the fault in arguments it singles out is theirdeductive invalidity. But this conception of fallacies turns out to beinadequate to cover the variety of the core fallacies in two ways: itis too narrow because it excludes begging the question which is notinvalid, and it is too wide because it condemns good but non-deductivearguments as fallacies (given that they also satisfy the appearancecondition) because they are invalid. Even if we replace the invaliditycondition in SDF with some less stringent standard of logical weaknesswhich could overcome the “too wide” problem, it wouldstill leave the difficulty of accounting for the fallacy of beggingthe question unsolved.

Siegel and Biro (1992, 1995) hold an epistemic account of fallacies,contrasting their view with dialectical/rhetorical approaches, becausematters extraneous to arguments, such as being a practice that leadsto false beliefs or not being persuasive, are not in their view asufficient condition to make an argument a fallacy. They take theposition that “it is a conceptual truth about arguments thattheir central … purpose is to provide a bridge from knowntruths or justified beliefs to as yet unknown … truths or asyet unjustified beliefs” (1992, 92). Only arguments that are“epistemically serious” can accomplish this; that is, onlyarguments that satisfy the extra-formal requirement that premises areknowable independently of their conclusions, and are more acceptableepistemically than their conclusions, can fulfill this function. Apurely logical approach to argument will not capture this requirementbecause arguments of the same valid form, but with different contents,may or may not be epistemically serious, depending on whether thepremises are epistemically acceptable relative to the conclusion.

Modifying Biro’s (1977, 265–66) examples we candemonstrate how the requirement of epistemic seriousness plays outwith begging the question. Consider these two arguments:

In the first argument the premises are knowable independently of theconclusion. The major premise can be deduced from other universalpremises about animals, and the minor premise, unlike the conclusionwhich must be inferred, can be known by observation. Hence, thisargument does not beg the question. However, in the second argument(due to Biro, 1977) given the minor premise, the major cannot be knownto be true unless the conclusion is known to be true. Consequently, onthe epistemic approach to fallacies taken by Biro and Siegel, thesecond argument, despite the fact that it is valid, is non-serious, itbegs the question, and it is a fallacy. If there was some independentway of knowing whether the major premise was true, such as that it wasa bylaw that only old Etonians could be committee members, theargument would be a serious one, and not beg the question.

Biro and Siegel’s epistemic account of fallacies isdistinguishable in at least three ways. First, it insists that thefunction of arguments is epistemic, and therefore anything that countsas a fallacy must be an epistemic fault, a breaking of a rule ofepistemic justification. But since logical faults are also epistemicfaults, the epistemic approach to fallacies will include logicalfallacies, although these must also be explicable in terms ofepistemic seriousness. Second, since the epistemological approach doesnot insist that all justification must be deductive, it allows thepossibility of their being fallacies (as well as good arguments) bynon-deductive standards, something precluded by SDF. Finally, wenotice that the appearance condition is not considered a factor inthis discussion of fallacies.

Ulrike Hahn and Mike Oaksford (2006a, 2006b) see themselves ascontributing to the epistemic approach to fallacy analysis bydeveloping a probabilistic analysis of the fallacies. It is part oftheir programme for a normative theory of natural languageargumentation. They are motivated by what they perceive as theshortcomings in other approaches. The logical (deductive) approachfalls short in that it simply divides arguments into valid and invalidarguments thereby failing to appreciate that natural languagearguments come in various degrees of strength. The alternativeapproaches to fallacies, given by procedural (dialectical) andconsensual accounts, they criticize on the basis that they fail toaddress the central problem raised by the fallacies: that of thestrength of the reason-claim complex. In Hahn and Oaksford’sview the strength or weakness of the classical fallacies (they areconcerned mostly with the post-Aristotelian ones) is not a result oftheir structure or their context of use. It is instead a matter of therelationship between the evidence and the claim (the contents of thepremises and the conclusion). Evaluation of this relationship isthought to be best captured by a probabilistic Bayesian account;accordingly, they adapt Bayes’ theorem to arguments evaluationwith the proviso that the probabilities are subjective degrees ofbelief, not frequencies. “An argument’s strength,”they write, “is a function of an individual’s initiallevel of belief in the claim, the availability and observation ofconfirmatory (or disconfirmatory) evidence, and the existence andperceived strength of competing hypotheses” (Corner, et al.1145). With Korb (2003) they view a fallacy as an argument with a lowprobability on the Bayesian model.

Since the variance in input probabilities will result in a range ofoutputs in argument strength, this probabilistic approach has thepotential to assign argument strengths anywhere between 0 and 1,thereby allowing that different tokens of one argument type can varygreatly in strength, i.e., some will be fallacies and others not.Also, and this seems to concur with our experience, different arguersmay disagree on the strength of the same arguments since they candiffer in the assignments of the initial probabilities. Hahn andOaksford also claim as advantages for their normative theory that itgives guidance for persuasion since it takes into account the initialbeliefs of audiences. Moreover, their approach contributes to thestudy of belief change; that is, to what extent our confidence in theconclusion changes with the availability of new evidence.

3.6 Dialectical/dialogical approaches to fallacies

Some of the most active new researchers on fallacies take adialectical and/or dialogical approach. This can be traced back toHamblin (1970, ch. 8) and Lorenzen’s (1969) dialogue theory. Thepanacea for fallacies that Whately recommended was more logic;Hamblin, however, proposed a shift from the logical to the dialecticalperspective.

[W]e need to extend the bounds of Formal Logic; to include features ofdialectical contexts within which arguments are put forward. To beginwith, there are criteria of validity of argument that are additionalto formal ones: for example, those that serve to proscribequestion-begging. To go on with, there are prevalent but falseconceptions of the rules of dialogue, which are capable of makingcertain argumentative moves seem satisfactory and unobjectionablewhen, in fact, they conceal and facilitate dialectical malpractice.(Hamblin 1970, 254)

The proposal here is to shift the study of fallacies from the contextsof arguments to the contexts of dialogues (argumentation), formulaterules for reasonable dialogue activity, and then connect fallacies tofailures of rule-following. Barth and Martens’s paper (1977),which studied theargumentum ad hominem by extendingLorenzen’s dialogue tableaux method to include the definitionsof the concepts “line of attack” and “winningstrategy,” leads to a conception of fallacies as either failuresto meet one of the necessary conditions of rational dialogicalargumentation, or failures to satisfy sufficient conditions asspecified by production rules of the dialogical method (1977, 96).

The Barth and Martens paper is a bridge between the earlier (quasi-)formal and subsequent informal dialectical theories, and is explicitlyacknowledged as a major influence by the Pragma-dialectical theory,the brainchild of Frans van Eemeren and Rob Grootendorst (1984).Rather than beginning from a logical or epistemological perspectivethey start with the role of argumentation in overcoming interpersonaldisagreements. The Pragma-dialecticians propose that inter-personalargumentation can be analysed as two-party-discussions having fouranalytical stages: a confrontation stage in which the participantsbecome aware of the content of their disagreement; an opening stage inwhich the parties agree (most likely implicitly) to shared startingpoints and a set of rules to govern the ensuing discussion; anargumentation stage wherein arguments and doubts about arguments areexpressed and recognized; and a final stage in which a decision aboutthe initial disagreement is made, if possible, based on what happenedin the argumentation stage.

The Pragma-dialectical theory stipulates a normative ideal of acritical discussion which serves both as a guide to thereconstruction of natural language argumentation, as well as astandard for the evaluation of the analysed product of reconstruction.A set of ten rules has been proposed as constitutive of thecritical-discussion ideal, and the proponents of the theory believethat rational arguers would accept them. If followed by both partiesto the disagreement, the rules constrain the argumentation decisionprocedure such that any resolution reached will be deemed reasonable,and “every violation of any of the rules of the discussionprocedure for conducting a critical discussion” will be afallacy (2004, 175). The rules range over all the four stages ofargumentation: at the confrontation stage there is a rule which saysone may not prevent the other party from expressing their view; forthe argumentation stage there is a rule which requires argumentationto be logically strong and in accord with one or another of threegeneral argumentation schemes; at the closing stage there is a rulethat the participants themselves are to decide which party wassuccessful based on the quality of the argumentation they have made:if the proponent carries the day, the opponent should acknowledge it,andvice versa.

The Pragma-dialectical theory proposes that each of the core fallaciescan be assigned a place as a violation of one of the rules of acritical discussion. For example, thead baculum fallacy is aform of intimidation that violates the rule that one may not attemptto prevent one’s discussion partner from expressing their views;equivocation is a violation of the rule that formulations in argumentsmust be clear and unambiguous;post hoc ergo propter hocviolates the rule that arguments must be instances of schemescorrectly applied. Moreover, on this theory, since any rule violationis to count as a fallacy this allows for the possibility that theremay be hitherto unrecognized “new fallacies.” Among thoseproposed aredeclaring a standpoint sacrosanct because thatbreaks the rule against the freedom to criticize points of view, andevading the burden of proof which breaks the rule that youmust defend your standpoint if asked to do so (see van Eemeren 2010,194).

Clearly not all the rules of critical discussions apply directly toarguments. Some govern other goal-frustrating moves which arguers canmake in the course of settling a difference of opinion, such asmis-allocating the burden of proof, asking irrelevant questions,suppressing a point of view, or failing to clarify the meaning ofone’s argumentation. In short, the Pragma-dialectical rules of acritical discussion are not just rules of logic or epistemology, butrules of conduct for rational discussants, making the theory more likea moral code than a set of logical principles. Accordingly, thisapproach to fallacies rejects all three of the necessary conditions ofSDF: a fallacy need not be an argument, thus the invalidity conditionwill not apply either, and the appearance condition is excludedbecause of its subjective character (Van Eemeren and Grootendorst2004, 175).

The Pragma-dialectical analysis of fallacies as rule-breakings in aprocedure for overcoming disagreements has recently been expanded totake account of the rhetorical dimension of argumentation.Pragma-dialectics takes the rhetorical dimension to stem from anarguer’s wish to have their view accepted which leads dialoguersto engage in strategic maneuvering vis-à-vis their dialoguepartners. However, this desire must be put in balance with thedialectical requirement of being reasonable; that is, staying withinthe bounds of the normative demands of critical discussions. The waysof strategic maneuvering identified are basically three: topicselection, audience orientation, and the selection of presentationaldevices, and these can be effectively deployed at each stage ofargumentation (Van Eemeren 2010, 94). “All derailments ofstrategic maneuvering are fallacies,” writes van Eemeren (2010,198), “in the sense that they violate one or more of the rulesfor critical discussion and all fallacies can be viewed as derailmentsof strategic maneuvering.” This means that all fallacies areultimately attributable to the rhetorical dimension of argumentationsince, in this model, strategic maneuvering is the entry of rhetoricinto argumentation discussions. “Because each fallacy has, inprinciple, sound counterparts that are manifestations of the same modeof strategic maneuvering” it may not appear to be a fallacy andit “may pass unnoticed” (Van Eemeren 2010, 199).Nevertheless, Pragma-dialectics prefers to keep the appearancecondition outside the definition of ‘fallacy’, treatingthe seeming goodness of fallacies as a sometime co-incidentalproperty, rather than an essential one.

Although the Pragma-dialectical theory continues to evolve into a moredetailed and comprehensive understanding of argumentation (vanEemeren, 2018, ch. 8), it maintains that the model of a criticaldiscussion can be used for argument appraisal across the variousfields in which argumentation takes place such as the legal, thepolitical, the interpersonal, etc. Each of the fields has developedits own stylized kind of discourse where different genres ofargumentation are favoured (adjudication, deliberation, mediation,etc.), but the reasonableness of arguments in any of the fields willdepend on how well they accord with the model of a criticaldiscussion. This approach has been challenged by Douglas Walton whohas written more about fallacies and fallacy theory than anyone else.He has published individual monographs on many of the well-knownfallacies, among them,Begging the Question (1991),Slippery Slope Arguments (1992),Ad HominemArguments (1998), and a comprehensive work on fallacy theory,A Pragmatic Theory of Fallacy (1995). Over the years hisviews have evolved. He has referred to his theory as “thePragmatic theory,” and like the Pragma-dialectical theory it hasa dialectical/dialogical basis; however, Walton envisions a number ofdistinct normative dialectical frameworks (persuasion dialogue,inquiry dialogue, negotiation dialogue, etc.) rather than the singlemodel of a critical discussion proposed by Pragma-dialectics.Postulating different kinds of dialogues with different startingpoints and different goals, thinks Walton, will bring argumentationinto closer contact with argumentation reality. At one point Waltonhad the idea that fallacies happened when there was an illicit shiftfrom one kind of a dialogue to another (1995, 118–23), forexample, using arguments appropriate for a negotiation dialogue in apersuasion dialogue, but more recently he has turned to other ways ofexplicating fallacies.

Although Walton recognizes the class of formal fallacies, his maininterest is in informal fallacies, especially the ones associated withargumentation schemes. The idea of an argumentation scheme is centralto Walton’s theory. Schemes are patterns of commonly used kindsof defeasible reasoning/argumentation such as appeals to expertopinion andad hominem arguments. Schemes do not identifyfallacies but rather argument kinds that are sometimes used fairly,and, other times, fallaciously. With each kind of scheme is associateda set of critical questions which guide us in deciding whether a givenuse of an argument is correct, weak or fallacious. So, if weconsider:

\(E\) is an expert in subject area \(S\);
\(E\) asserts \(p\) based on \(E\)’s knowledge of \(S\);
So, \(p\).

to be the scheme for the appeal-to-expertise kind of argument,^[8] then there will be a question for each premise: Is \(E\) really anexpert in \(S\)? Did \(E\) say \(p\) when s/he was acting in her/hisprofessional capacity? (… or did s/he blurt it out while drunkat an association party?). If the answer to both questions is Yes,then the argument creates a presumption for the conclusion—butnot a guarantee, for the reasoning is defeasible: other informationmay come to light that will override the presumption. If one of thequestions cannot be answered clearly this is an indication that theargument is weak, and answering No to either of the two questionscancels the presumption for the conclusion, i.e., makes the argumentinto a bad argument from expert opinion. If the bad argument has“a semblance of correctness about it in [the] context, and posesa serious obstacle to the realization of the goal of thedialog,” then it is a fallacy (2011, 380).^[9]

The definition of fallacy Walton proposes (1995, 255) has five parts.A fallacy:

1. an argument (or at least something that purports to be anargument) that
2. falls short of some standard of correctness;
3. is used in a context of dialogue;
4. has a semblance of correctness about it; and
5. poses a serious problem to the realization of the goal of thedialogue.

Here we find that Walton has relaxed two of the necessary conditionsof SDF. Purporting to be an argument is enough (it doesn’treally have to be an argument), while falling short of a standard (onethat will vary with the kind of dialogue under consideration) replacesthe invalidity condition. However, the appearance condition, hereexpressed as fallacies having a semblance of correctness about them,remains in full force. The two extra conditions added to fallacy arethat they occur only in contexts of dialogue and that they frustratethe realization of the goal of the kind of dialogue in which theyoccur. In insisting on this dialogical dimension, Walton is in fullsympathy with those who think that fallacies can only be rightlyanalysed within a dialectical framework similar to the ones Aristotleoriginally studied, and later better defined by Hamblin and Lorenzen.Walton volunteers a shorter version of the definition of a fallacy as“a deceptively bad argument that impedes the progress of adialogue” (1995, 256).

Walton divides fallacies into two kinds: paralogisms and sophisms. Aparalogism is “the type of fallacy in which an error ofreasoning is typically committed by failing to meet some necessaryrequirement of an argumentation scheme” whereas “thesophism type of fallacy is a sophistical tactic used to try tounfairly get the best of a speech partner in an exchange ofarguments” (2010, 171; see also 1995, 254). Paralogisms areinstances of identifiable argumentation schemes, but sophisms are not.The latter are associated more with infringing a reasonableexpectation of dialogue than with failing some standard of argument(2011, 385; 2010, 175). A further distinction is drawn betweenarguments used intentionally to deceive and arguments that merelybreak a maxim of argumentation unintentionally. The former count asfallacies; the latter, less condemnable, are blunders (1995, 235).

Among the informal paralogisms Walton includes:ad hominem,ad populum,ad misericordiam,adignorantiam,ad verecundiam, slippery slope, falsecause, straw man, argument from consequences, faulty analogy,composition and division. In the category of sophisms he placesadbaculum, complex question, begging the question, hastygeneralization,ignoratio elenchi, equivocation, amphiboly,accent, andsecundum quid. He also has a class of formalfallacies very much the same as those identified by Whately and Copi.The largest class in Walton’s classification is the oneassociated with argumentation schemes andad-arguments, andthese are the ones that he considers to be the most central fallacies.Nearly all the Aristotelian fallacies included find themselvesrelegated to the less studied categories of sophisms. Taking a longlook at the history of fallacies, then, we find that the Aristotelianfallacies are no longer of central importance. The main focus ofinterest is now the list of fallacies that have grown out ofLocke’s creation of thead-argument genre.

Another recent approach comes from virtue argumentation theory(modelled on virtue epistemology). Virtue argumentation theory ischaracterized by a distinct set of virtues thought to be essential togood argumentation: willingness to engage in argumentation,willingness to listen to others and willingness to modify one’sown position (see, e.g., Cohen 2009). These may be supplemented withepistemic virtues and even in some cases moral virtues. Althoughvirtues and vices are dispositions of arguers and fallacies arearguments, it is claimed that good argumentation generally resultsfrom the influence of argumentation virtues and bad argumentation(including the fallacies) arise because of the vices of arguers.

Taking the Aristotelian view that virtues are a mean between oppositekinds of vices, fallacious arguments can be seen as resulting fromarguers moving in one or another direction away from a mean of goodargumentation. Aberdein (2013, 2016) especially has developed thismodel for understanding many of the fallacies. We can illustrate theview by considering appeals to expertise: the associated vices mightbe too little respect for reliable authorities at one extreme and toomuch deference to authorities at the other extreme. Aberdein developsthe fallacies-as-argumentation-vices analysis in some detail for otherof the ad-arguments and sketches how it might be applied to the othercore fallacies, suggesting it can profitably be extended to all ofthem.

All the fallacies, it is claimed, can be fitted in somewhere in theclassification of argumentational vices, but the converse is not truealthough it is possible to bring to light other shortcomings to whichwe may fall prey in argumentation. Another aspect of the theory isthat it distributes argumentation vices among both senders andaudiences. Speakers may infect their arguments with vices when theyare, for example, closed minded or lack respect for persons, andaudiences can contribute to fallaciousness by letting theirreceptivity be influenced by naïvety, an over-reliance on commonsense, or an unfounded bias against a speaker. Perhaps the developmentof the virtue argumentation theory approach to fallacies provides asupplement to Mill’s theory of fallacies. He distinguished(1891, V, i, 3) what he called the moral (dispositional) andintellectual causes of fallacy. The study of the argumentative vicesenvisioned above seems best included under the moral study offallacies as the vices can be taken to be the presdisposing causes tocommit intellectual mistakes, i.e., misevaluations of the weight ofevidence.

Finocchiaro (2023, 24) has introduced a distinction betweenground-level arguments and meta-argument. The former are about naturalphenomena, historical events, human actions, abstract entities, etc.and the latter are about one or more arguments, or about argumentationin general. When we justify our judgments that an argument,x, has committed a fallacy we are making a meta-argumentaboutx. Finocchiaro uses the fallacy of composition as anexample saying it is primarily a meta-argument concept used to assessan argument at the ground-level as a fallacy.

Akin and Casey take this line of analysis further, arguing that thereare indeed fallacies best understood as fallacies ofmeta-argumentation. They have studied three of them: the straw manfallacy (2022a), bothsiderism (2022b), and what they call thefree-speech fallacy (2023). These are all fallacies that may occur inthe process of argumentation, i.e., exchanges between arguers. On thisview, straw man fallacies happen when someone in the course ofargumentation inaccurately and unfavourable distorts a ground-levelargument in an attempt to refute it or discredit its source. In thecase of bothsiderism, there are conflicting arguments each drawing onprima facie evidence. This can lead to the meta-argument that thetruth lies somewhere in the middle between the opposed ground-levelconclusions. This is considered a fallacy because purported contraryevidence noticed at the meta-level is insufficient reason to abandonboth the ground-level conclusions in favour of a compromise. Caseswhere people claim their right to free speech is infringed, say Akinand Casey, also admit of the possibility of meta-argumentationfallacies. One of the ways is when criticism of a view is mistaken forcensorship of that view; another is when parties are excluded fromparticipation in a discussion for good reasons such as lack ofqualifications or holding repugnant social views. From their exclusionthey may make the meta-argument that the outcome of the discussion isepistemically unwarranted because of evidence not taken intoconsideration, or they may even think that the fact that their viewwas excluded is a sign that it has merit its opponents would rathernot admit. The authors say that these kinds of mistakes aremeta-argumentation fallacies and anticipate that there are more ofthem waiting for analysis.

4. Current issues in fallacy theory

4.1 The nature of fallacies

A question that continues to dog fallacy theory is how we are toconceive of fallacies. There would be advantages to having a unifiedtheory of fallacies. It would give us a systematic way of demarcatingfallacies and other kinds of mistakes; it would give us a frameworkfor justifying fallacy judgments, and it would give us a sense of theplace of fallacies in our larger conceptual schemes. Some generaldefinition of ‘fallacy’ is wanted but the desire isfrustrated because there is disagreement about the identity offallacies. Are they inferential, logical, epistemic or dialecticalmistakes? Some authors insist that they are all of one kind: Biro andSiegel, for example, that they are epistemic, and Pragma-dialecticsthat they are dialectical. There are reasons to think that allfallacies do not easily fit into one category.

Together theSophistical Refutations and Locke’sEssay are the dual sources of our inheritance of fallacies.However, for four reasons they make for uneasy bedfellows. First, thead fallacies seem to have a built-in dialectical character,which, it can be argued, Aristotle’s fallacies do not have (theyare not sophistical refutations but arein sophisticalrefutations). Second, Aristotle’s fallacies are logicalmistakes: they have no appropriate employment outside eristicargumentation whereas thead-fallacies are instances ofad-arguments, often appropriately used in dialogues. Third,the appearance condition is part of the Aristotelian inheritance butit is not intimately connected with thead-fallaciestradition. A fourth reason that contributes to the tension between theAristotelian and Lockean traditions in fallacies is that the formergrew out of philosophical problems, largely what are logical andmetaphysical puzzles (consider the many examples inSophisticalRefutations), whereas thead-fallacies are more gearedto social and political topics of popular concern, the subject matterthat most intrigues modern researchers on fallacy theory.

As we look back over our survey we cannot help but observe thatfallacies have been identified in relation to some ideal or model ofgood arguments, good argumentation, or rationality. Aristotle’sfallacies are shortcomings of his ideal of deduction and proof,extended to contexts of refutation. The fallacies listed by Mill areerrors of reasoning in a comprehensive model that includes bothdeduction and induction. Those who have defended SDF as the correctdefinition of ‘fallacy’^[10] take logicsimpliciter or deductive validity as the ideal ofrationality. Informal logicians view fallacies as failures to satisfythe criteria of what they consider to be a cogent argument. Defendersof the epistemic approach to fallacies see them as shortfalls of thestandards of knowledge-generating arguments. Finally, those who areconcerned with how we are to overcome our disagreements in areasonable way will see fallacies as failures in relation to ideals ofdebate or critical discussions.

The standard treatment of the core fallacies has not emerged from asingle conception of good argument or reasonableness but rather, likemuch of our unsystematic knowledge, has grown as a hodgepodgecollection of items, proposed at various time and from differentperspectives, that continues to draw our attention, even as thestandards that originally brought a given fallacy to light areabandoned or absorbed into newer models of rationality. Hence, thereis no single conception of good argument or argumentation to bediscovered behind the core fallacies, and any attempt to force themall into a single framework, must take efforts to avoid distorting thecharacter originally attributed to each of them.

4.2 The appearance condition

From Aristotle to Mill the appearance condition was an essential partof the conception of fallacies. However, some of the new,post-Hamblin, scholars have either ignored it (Finocchiaro, Biro andSiegel) or rejected it because appearances can vary from person toperson, thus making the same argument a fallacy for the one who istaken in by the appearance, and not a fallacy for the one who seespast the appearances. This is unsatisfactory for those who think thatarguments are either fallacies or not. Appearances, it is also argued,have no place in logical or scientific theories because they belong topsychology (van Eemeren and Grootendorst, 2004). But Walton (e.g.,2010) continues to consider appearances an essential part of fallaciesas does Powers (1995, 300) who insists that fallacies must “havean appearance, however quickly seen through, of being valid.” Ifthe mistake in an argument is not masked by an ambiguity that gives itthe appearance of being a better argument than it really is, Powersdenies it is a fallacy.

The appearance condition of fallacies serves at least two purposes.First, it can be part of explanations of why reasonable people makemistakes in arguments or argumentation: it may be due in part to anargument’s appearing to be better than it really is. Second, itserves to divide mistakes into two groups: those which are trivial orthe result of carelessness (for which there is no cure other thanpaying better attention), and those which we need to learn to detectthrough an increased awareness of their seductive nature. Without theappearance condition, it can be argued, no division can be madebetween these two kinds of errors: either there are no fallacies orall mistakes in argument and/or argumentation are fallacies; aconclusion that some are willing to accept, but which runs contrary totradition. One can also respond that there is an alternative to usingthe appearance condition as the demarcation property between fallaciesand casual mistakes, namely, frequency. Fallacies are those mistakeswe must learn to guard against because they occur with noticeablefrequency. To this it may be answered that ‘noticeablefrequency’ is vague, and is perhaps best explained by theappearance condition.

Oswald and Herman (2020) explain the possibility that an argumentmight seem better than it really is by appealing to both cognitive andrhetorical factors. The cognitive factor is that the information setof a sender making a fallacious argument might be greater than theinformation set of an argument receiver, thus potentially putting thereceiver in a position to be deceived. Persuasive skills can exploitsuch a difference in information sets by manipulating the relevantcontextual evidence; that is, by bringing forward what favours thefallacious argument and holding back critical factors against it. Thereceiver may thus be taken in by a fallacy because of the way theargument was presented to them. Hansen (2023) considers the causalfactors that might lead to misperception of bad arguments as goodarguments. They include structural properties of arguments, perceptualperspectives, the social atmosphere in which the arguments arepresented, and misperceptions due to abnormalities in the argumentreceiver.

4.3 Teaching

On the more practical level, there continues to be discussion aboutthe value of teaching the fallacies to students. Is it an effectiveway for them to learn to reason well and to avoid bad arguments? Onereason to think that it is not effective is that the list of fallaciesis not complete, and that even if the group of core fallacies wasextended to incorporate other fallacies we thought worth including, wecould still not be sure that we had a complete prophylactic againstbad arguments. Hence, we are better off teaching the positive criteriafor good arguments/ argumentation which give us a fuller set ofguidelines for good reasoning. But some (Pragma-dialectics and Johnsonand Blair) do think that their stock of fallacies is a complete guardagainst errors because they have specified a full set of necessaryconditions for good arguments/argumentation and they hold thatfallacies are just failures to meet one of these conditions.

Another consideration about the value of the fallacies approach toteaching good reasoning is that it tends to make students overlycritical and lead them to see fallacies where there are not any;hence, it is maintained we could better advance the instilling ofcritical thinking skills by teaching the positive criteria of goodreasoning and arguments (Hitchcock, 1995). In response to this view,it is argued that, if the fallacies are taught in a non-perfunctoryway which includes the explanations of why they arefallacies—which normative standards they transgress—then acourse taught around the core fallacies can be effective in instillinggood reasoning skills (Blair 1995).

In more recent work, Blair (2023) has moved closer toHitchcock’s recommendation that fallacies not be taught inintroductory level courses, but his reason is that the study offallacies has become so complex with many dimensions and overlappingapproaches that it has become a subject too challenging forundergraduate students; moreover, few instructors are familiar withthe extensive literature that has developed on fallacies. Hitchcock(2023) has followed up his earlier article with a study of six of themost widely used textbooks (each having at least ten editions) thathave a section on the fallacies and asked whether they have benefittedfrom Hamblin’s (1970) critique of the standard treatment (seeabove section 3.1). He finds that by the standard implicit inHamblin’s critique, there has been little improvement in theanalysis and presentation of fallacies in those textbooks.

4.4 Biases

Biases are “inclinations to see things one way rather thananother,” explains Nickerson (2021, 208). He reviews theliterature on biases that can affect reasoning, discussing both themotivational and cognitive factors that may lead to the presence ofbiases (ch. 7). Like fallacies, there is no fixed definitive list, andthe individuation of biases largely depends on the goal of ourinquiries. Correia (2011) has taken Mill’s insight that biasesare predisposing causes of fallacies a step further by connectingidentifiable biases with particular fallacies. Biases can influencethe committing of fallacies even where there is no intent to bedeceptive, he observes. Taking biases to be “systematic errorsthat invariably distort the subject’s reasoning andjudgment,” the picture drawn is that particular biases areactivated by desires and emotions (motivated reasoning) and once theyare in play, they negatively affect the fair evaluation of evidence.Thus, for example, the “focussing illusion” bias inclinesa person to focus on just a part of the evidence available, ignoringor denying evidence that might lead in another direction. Correia(2011, 118) links this bias to the fallacies of hasty generalizationand straw man, suggesting that it is our desire to be right thatactivates the bias to focus more on positive or negative evidence, asthe case may be. Other biases he links to other fallacies.

Thagard (2011) is more concerned to stress the differences betweenfallacies and biases than to find connections between them. He claimsthat the model of reasoning articulated by informal logic is not agood fit with the way that people actually reason and that only a fewof the fallacies are relevant to the kinds of mistakes people actuallymake. Thagard’s argument depends on his distinction betweenargument and inference. Arguments, and fallacies, he takes to beserial and linguistic, but inferences are brain activities and arecharacterized as parallel and multi-modal. By “parallel”is meant that the brain carries out different processessimultaneously, and by “multi-modal” that the brain usesnon-linguistic and emotional, as well as linguistic representations ininferring. Biases (inferential error tendencies) can unconsciouslyaffect inferring. “Motivated inference,” for example,“involves selective recruitment and assessment of evidence basedon unconscious processes that are driven by emotional considerationsof goals rather than purely cognitive reasoning” (2011, 156).Thagard volunteers a list of more than fifty of these inferentialerror tendencies. Because motivated inferences result from unconsciousmental processes rather than explicit reasoning, the errors ininferences cannot be exposed simply by identifying a fallacy in areconstructed argument. Dealing with biases requires identification ofboth conscious and unconscious goals of arguers, goals that can figurein explanations of why they incline to particular biases.“Overcoming people’s motivated inferences,” Thagardconcludes, “is therefore more akin to psychotherapy thaninformal logic” (157), and the importance of fallacies isaccordingly marginalized.

In response to these findings, one can admit their relevance to thepedagogy of critical thinking but still recall the distinction betweenwhat causes mistakes and what the mistakes are. The analysis offallacies belongs to the normative study of arguments andargumentation, and to give an account of what the fallacy in a givencase is will involve making reference to some relevant norm ofargument or argumentation. It will be an explanation of what themistake in the argument is. Biases are relevant to understanding whypeople commit fallacies, and how we are to help them get past them,but they do not help us understand what the fallacy-mistakes are inthe first place—this is not a question of psychology. Continuedresearch at this intersection of interests will hopefully shed morelight on both biases and fallacies.

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Other Internet Resources

• Curtis, Gary N.,Fallacy Files
• Dowden, Bradley,Fallacies, entry in theInternet Encyclopedia of Philosophy.
• Hansen, H.V., and C. Fioret, 2016.A searchable bibliography of fallacies—2016,Informal Logic, 36: 432–72.
• Informal Logic, an open-access journal.
• Labossiere, Michael C.,Fallacies, hosted by The Nizkor Project.
• RAIL, a blog about Reasoning, Argumentation, and Informal Logic.

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