ISSA Proceedings 2006 – Why There Is No Argumentum Ad Hominem Fallacy

Contemporary introductions to logic (e.g. Hurley 2003: 118-121, Copi & Cohen 2002: 143-145) typically treat the argumentum ad hominem as a fallacy of relevance. It is said to consist generically in a response to someone’s statement or argument by an attack on that person. The abusive ad hominem is pure abuse; it points out some fault of character or intellect in the opponent. The circumstantial ad hominem is tied more specifically to the content of the opponent’s discourse; it alleges some self-interested motive or dogmatic bias as the source of the opponent’s position. The tu quoque responds to a criticism of behaviour by pointing out that the critic has previously engaged in that very behaviour. All three types of personal attack, the textbooks typically say, are irrelevant to the merits of the opponent’s position. Thus all three are fallacies. To show that someone’s statement or argument is inadequate, one must point out substantively what is wrong with it. Personal attack is logically otiose.

On the contrary, I shall argue, there is no such thing as an ad hominem fallacy.
What is a fallacy? Trudy Govier nicely sums up the standard conception of a fallacy in the western logical tradition, as follows: “By definition, a fallacy is a mistake in reasoning, a mistake which occurs with some frequency in real arguments and which is characteristically deceptive.” (Govier 1995: 172) If there is an ad hominem fallacy, as opposed to an argumentum ad hominem which is sometimes legitimate and sometimes not, it should according to this definition be a move in argument or reasoning. Further, it should be always mistaken; a move that is sometimes legitimate and sometimes mistaken is not a fallacy. Further, it should occur with some frequency in real arguments. A mistake in an unrealistic invention of a logic textbook writer, designed to fit the textbook’s theory, does not amount to a fallacy, for a mistake is not a fallacy unless people actually make it. To support a claim that a certain mistake is a fallacy, one therefore needs to point to actual examples, and one’s analysis of these examples as committing the mistake needs to be defensible, i.e. accurate and fair. Further, one needs to show that people are taken in by this mistake; thus, sophisms that would fool nobody are not fallacies.
Contrapositively, to show that a certain move is not a fallacy, one needs to show only that one of the necessary conditions for fallaciousness is lacking. Perhaps the move is not even a way of reasoning or arguing. Perhaps it is not a mistake, or not always a mistake. Perhaps people do not actually make this move in real arguments, at least not with enough frequency to deserve the invention of a label and a listing in the pantheon of logical fallacies. Or, if the move does occur with some frequency, perhaps it is so patently absurd that it would not fool anybody with even a minimum of logical acuity. Any of these four possibilities would be enough to show that the move in question is not a fallacy.
The reasons for the non-fallaciousness of the argumentum ad hominem vary from one species to another. I shall therefore consider each species separately, in each case giving some historical background.

1. The Traditional Sense of the Ad Hominem
In western thought, to argue ad hominem (Greek pros ton anthrÇpon) originally meant to use the concessions of an interlocutor as a basis for drawing a conclusion, thus forcing the interlocutor either to accept the conclusion or to retract a concession or to challenge the inference. Aristotle in his discussion of the principle of non-contradiction distinguishes “absolute proof” (haplÇs apodeixis) from “proof relative to this person” (pros tonde apodeixis, Metaphysics XI.5.1062a3). In his influential 13th century commentary on this work (Lectio V. n. 2213, 2219, 2222; cited in Nuchelmans [1993: 40, n. 9]), Thomas Aquinas uses the corresponding Latin phrase demonstratio ad hominem for relative proofs of first principles. By the 17th century, logic textbooks were using the phrases “argumentum ad hominem” and “argumentatio ad hominem” quite generally for arguing about any subject-matter at all from the concessions of one’s interlocutor, a usage attested as a scholastic commonplace (Nuchelmans 1993: 41); in the same century, Galileo uses the expression “ad hominem” for an argument whose author derives a conclusion not acceptable to an opponent from premisses accepted or acceptable by the opponent but not the arguer (Finocchiaro 1973-74). John Locke is referring to this background when he reports in his essay Concerning Human Understanding, first published in1689, that “to press a man with consequences drawn from his own principles or concessions … is already known under the name of argumentum ad hominem” (Locke 1959/1689: 278; IV.XVII.21).

In this whole tradition, which continued in logic textbooks of the 18th and 19th century (Nuchelmans 1993), there is not a hint that an argumentum ad hominem is a personal attack. It is not an argument against the opponent, but an argument to the opponent, i.e. to the commitments already made by the opponent, whether by unprompted assertion or by concession in response to a question. It is a perfectly legitimate way for a proponent to get the opponent to accept the consequences of those commitments, even if the proponent does not share them. It is not in itself mistaken, merely of limited probative value.
One would make a mistake in reasoning if one represented such an argument ad hominem as an absolute proof of its conclusion. And in fact this misrepresentation is how Richard Whately (1827/1826) defines the ad hominem fallacy – apparently the first time in a logical tradition going back more than 23 centuries that arguing ad hominem was stigmatized as fallacious. A fallacy is committed, Whately claims, if (and apparently only if) an argumentum ad hominem is presented as having established the conclusion absolutely, rather than merely as one that the individual referred to is bound to admit. But it is confusing to describe this mistake as an ad hominem fallacy while at the same time maintaining that the argumentum ad hominem on which it is based is non-fallacious. Parry and Hacker (1991) have coined the phrase illicit metabasis for the mistake of claiming on the basis of an argumentum ad hominem to have proved the conclusion to someone other than the opponent. The mistake here is in the misrepresentation of a legitimate argumentum ad hominem. It may of course be doubted whether the mistake occurs often enough, and is deceptive enough, to be dignified with the label of a fallacy. Certainly most contemporary logic textbooks do not mention this error in their list of fallacies.

2. The Tu Quoque
Two writers from the early 19th century testify to a further broadening of the phrase “argumentum ad hominem” to cover arguments from the conduct or character of one’s opponent. In his 1826 Elements of Logic, Richard Whately represents unnamed “logical writers” as describing the argumentum ad hominem in “lax and popular language” as “addressed to the peculiar circumstances, character, avowed opinions, or past conduct of the individual”, and as thus referring to him only and not bearing directly and absolutely on the real question (Whately 1827/1826: 191). Schopenhauer (1951/ca. 1826-1831), writing at about the same time, extends the concept of a proof ad hominem to proof from an opponent’s actions. Such a proof may point out an apparent inconsistency between present words and previous deeds, as in Whately’s famous sportsman’s rejoinder: A sportsman accused of barbarity in killing unoffending hares or trout for his amusement “not unjustly” shifts the burden of proof to the accusers with the rejoinder, “Why do you feed on the flesh of animals?” (Whately 1827/1826: 192). The rejoinder establishes a presumption that the accusers are bound by their flesh-eating conduct to admit that there is nothing wrong with killing unoffending animals for sport. With the presumption established, the flesh-eating critics must now establish a relevant difference between killing animals for food and killing them for sport.

In its use to turn an opponent’s criticism on himself, this form of argument appears in 21st century logic textbooks as the “tu quoque” (you too). It can be deployed erroneously, for example by misdescribing the past actions of one’s critic, alleging an inconsistency where there is none, or representing the opponent’s proposition as refuted absolutely when it is in fact refuted only ad hominem. But these mistakes are ways in which a perfectly legitimate form of argument can be manipulated. The error is not a tu quoque fallacy or an ad hominem fallacy, but a fallacy of misrepresentation (“straw man”), false allegation of inconsistency, or illicit metabasis. Properly used, the tu quoque puts a reasonable burden on a critic to explain away an apparent inconsistency between word and deed. As a paradigm case, we may look at the following passage quoted by Engel:
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I am a Newfoundlander, and I cannot help but feel some animosity toward those people who approach the seal hunt issue from a purely emotional stance. Surely this is not the way they look in their butcher’s freezer, when they are looking for pork chops. Yet the slaughtering method approved by the Department of Health officials for swine is hideous, and nowhere near as humane as the dispatching of a young seal. (Engel 1994: 31)

This passage is a tu quoque addressed to a third party: it alleges that the critics of the seal hunt support even less humane means of killing animals, by eating pork. Hurley (2003, p. 119) claims that the tu quoque is an irrelevant attempt to show that the premisses of an opponent’s argument do not support its conclusion. Hurley’s analysis clearly does not fit our passage, which makes no reference to the emotional critics’ arguments. Copi and Cohen (2002, p. 144), on the other hand, treat the tu quoque (which they label a species of circumstantial ad hominem) as an irrelevant attempt to show on the basis of the opponent’s previous actions that the opponent’s claim is false – in effect, Whately’s ad hominem fallacy extended to arguments from an opponent’s actions. The Copi-Cohen analysis does not fit our passage either, since the author does not take the critics’ inconsistency to establish that the seal hunt should be allowed, but rather uses it to explain his animosity towards them. The appeal to apparent inconsistency has the same function as Whately’s sportsman’s rejoinder: it puts the critics on the defensive.
Our passage is typical in this respect. Fairly interpreted, real instances of the tu quoque are in principle legitimate. It would of course be a logical mistake to take an inconsistency between an opponent’s words and deeds to show that the conclusion of the opponent’s argument does not follow from its premisses, or to show that the words are incorrect. But that is not what happens with real instances of the tu quoque. Real cases are legitimate attempts to put an opponent on the spot by pointing out an apparent inconsistency between word and deed.

3. The Abusive Ad Hominem
The abusive argumentum ad hominem seems to have emerged from an amalgamation of traditions stemming from two remarks of Aristotle.
In his Sophistical Refutations Aristotle distinguishes two ways in which one may “solve” a fallacious argument. The proper way is relative to the argument (pros ton logon, 177b34, 178b17): the solution will work for all instances of the fallacy and is independent of the particular commitments of the argument’s author. To depend on the author granting some proposition is to propose “a solution relative to the man” (lusis pros ton anthrôpon, 178b17), a phrase translated into Latin by Boethius as “solutio ad hominem”. Apparently following Boethius, logical treatises of the 12th and 13th century use “solutio ad hominem” for a pseudo-solution of a fallacy that attacks the questioner instead of his faulty argument (Nuchelmans 1993: 43).
In his Rhetoric Aristotle complains that writers of rhetorical handbooks in his day paid no attention to its subject-matter, persuasion, but focused on accessories “outside the thing” (exô tou pragmatos, I.1.1354a15-16). Appropriating this notion, later ancient rhetorical writers identified one such feature as the person of the disputant, thus setting up a contrast between the person or man (Latin persona, homo) and the business or cause or thing (Latin negotium, causa, res) (Nuchelmans 1993: 43-44). Features of a speech that point out unsavoury personal characteristics of one’s opponent were generally respectable, as long as they were effective in persuading the audience. Such a rhetorical ad personam or ad hominem would typically appear in the refutation section of a speech (Latin refutatio, confutatio, solutio) after one’s proof, in which case it could be given the name “solutio ad hominem”.
The dialectical and the rhetorical solutio ad hominem came together in a number of logical treatises of the 15th and 16th centuries. The solutio ad rem, characterized as a genuine refutation of a bad argument, was contrasted to a solutio ad hominem, which could consist either in repelling an adversary (whether by making a counter-charge or by arguing that it was inappropriate for him to utter his accusation) or in trivializing the offence with which one was charged or in inserting a digression. These treatises tended to disparage such devices as not belonging to logic, though they did not stigmatize them as fallacies (Nuchelmans 1993: 44-46).

In the late 19th and early 20th century, perhaps influenced by this tradition, introductory logic textbooks (e.g. Jevons 1882, Joseph 1906, Sellars 1917, Cohen & Nagel 1934, Beardsley 1950, Copi 1953) began to use the phrase argumentum ad hominem not in Locke’s and Whately’s dialectical sense of arguing from an opponent’s concessions or other commitments, but in the rhetorician’s sense of a response to an opponent with a personal attack, and to stigmatize it as a fallacy. This shift appears to have happened by means of a slide from Whately’s (1827/1826) extended sense of argumentum ad hominem. The argumentum ad hominem appears in the plural in Augustus De Morgan’s Formal Logic, which was first published in 1847, accompanied by the claim that argumenta ad hominem generally commit the fallacy of ignoratio elenchi, characterized as answering to the wrong point (De Morgan 1847, pp. 308-309). De Morgan describes argumenta ad hominem as arguments with some reference to the person to whom the argument is addressed, a loose characterization that covers both arguments ex concessis and personal attack arguments. It is noteworthy that he does not claim that an argumentum ad hominem is in itself a fallacy, only that in context it generally commits the fallacy of answering to the wrong point. As species of argumenta ad hominem De Morgan mentions recrimination, charge of inconsistency and parallel cases – the latter illustrated by Whately’s sportsman’s rejoinder, which De Morgan argues is not really a parallel case. Jevons (1882, pp. 178-179) simplifies De Morgan’s claim by classifying the argumentum ad hominem, defined as “an argument which rests, not upon the merit of the case, but the character or position of those engaged in it”, as in itself a species of irrelevant conclusion, which “consists in arguing to the wrong point, or proving one thing in such a manner that it is supposed to be something else that is proved”. He gives as examples the barrister following the solicitor’s advice, “No case; abuse the plaintiff’s attorney”; a man accused of a crime saying that the prosecutor is as bad; and an argument that the proposer in Parliament of a change in the law is not the man to bring it forward. Thus the shift from the traditional dialectical sense of argumentum ad hominem to the contemporary abusive sense is complete. As one example of the abusive argumentum ad hominem, we may take the following letter to the editor:
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Re: Emotional Bardot Makes Plea For Seals (March 23): Is Brigitte Bardot really the compassionate crusader she claims to be?
A quick Google search reveals that she has been found guilty of inciting hatred at least four times by French courts in recent years. Her most recent conviction was in 2004, for remarks in her book, A Scream in the Silence, that viciously attacked gays, Muslims, immigrants and the unemployed. She considers homosexuals to be “fairground freaks” and opposes interracial marriage. Her political hero is Jean-Marie Le Pen, the extreme-right National Front leader. This is the champion that animal activists have brought to teach Canadians about ethics and compassion? (Alan Herscovici, executive vice-president, Fur Council of Canada, Montreal, The Globe and Mail, 24 March 2006)

The function of this letter is to undermine the standing of the famous French actress as a spokesperson for opposition to the seal hunt. It marshals evidence that in many respects she is not a compassionate person. Her alleged lack of compassion for various groups of human beings does not address her position that the annual seal hunt in Canada should be abolished, or its supporting arguments. In fact, however, media reports attributed no arguments to Bardot, only an appeal to stop what she called a “massacre” and a failed attempt to deliver her message personally to the Canadian prime minister. Since her celebrity was the chief basis for the media attention to her appeal, it is a relevant response to question her standing on this issue, what rhetoricians following Aristotle call her ethos. Brinton (1985, 1995) has ably defended the traditional rhetorical position that such attacks on an opponent’s ethos are relevant, and not fallacious.

A rather different example of the abusive argumentum ad hominem occurred in an exchange in the Canadian House of Commons in 1970, reported by Walton (1985: 203-204). The prime minister was asked if he would consider using a certain government plane, the Jet-star, to send an information-gathering team to Biafra. He responded as follows:
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Mr. Trudeau: It would have to refuel in the middle of the Atlantic Ocean…
Mr. Hees: On a point of order, Mr. Speaker, I bought the plane for the government and I know it can make the flight with the proper stops on the way…
Mr. Trudeau: I do not think it would have to stop if the hon. Member went along and breathed into the tank.

The prime minister insinuates that Mr. Hees is habitually drunk. Walton in his commentary on this example construes the insinuation as an argument that Hees’ argument should not be taken seriously. But, in the first place, Hees has not made an argument, just a statement. Secondly, to say the least, it is not at all obvious that the prime minister has alluded to the alleged drinking habits of Mr. Hees in order to show that Mr. Hees’ statement is false. The attack is a diversion, making a joke at Hees’ expense rather than acknowledging the correctness of Hees’ point and retracting his (Trudeau’s) previous statement. It has no probative force, and appears to have no probative intent.

Perhaps the most careful textbook discussion of the abusive ad hominem occurs in Johnson and Blair’s Logical Self-Defense (Johnson & Blair 1977, 1983, 1993). The authors quote real examples, describe their context, and discuss in a nuanced way whether the passage commits the fallacy as they understand it. In the most recent edition of their textbook (1993, pp. 88-93), they characterize the fallacy as committed when two conditions are met:
1. The critic responds to the position of an arguer by launching a personal attack on the arguer, ignoring the arguer’s position.
2. The personal attack on the arguer can be shown to be irrelevant to the assessment of the argument.

On the conception of fallacy used in this article, such a personal attack is a fallacy only if it amounts to a piece of reasoning that the arguer’s argument or position should be rejected. If the attack has a purely diversionary function, as does Trudeau’s response to Hees in the example just discussed, it may be reprehensible, but it is not a fallacy, because it is not a mistake in reasoning. (A possible exception would be a diversionary personal attack in a rule-governed dialogical game in which the rules required the attacker to respond substantively to the opponent’s position or argument.) In their (1993), Johnson and Blair analyse five passages (pp. 88-91, 305) which they take to commit an ad hominem fallacy. These passages satisfy the two conditions just quoted. In my opinion, however, none of them is fairly interpreted as committing a fallacy in the sense defined in this article. For reasons of space, I shall discuss just one of their passages, an excerpt from a review in the magazine Rolling Stone of Allan Bloom’s 1987 best-seller The Closing of the American Mind. In the book, Bloom criticizes rock music as contributing through its overt sexuality to an overall climate of promiscuity. The reviewer wrote the following:
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Bloom’s attack is inane. Still the professor is correct about one important distinction between the kids of the 50s and those of the 80s: in the 50s the kids talked endlessly about sex; today the young people actually do it. This seems to drive the 56-year-old Bloom – who is still a bachelor – crazy. Bloom denounces Jagger with such relish that one may wonder if the professor himself is turned on by Mick’s pouty lips and wagging butt.

Following their two-pronged strategy, Johnson and Blair first note that this response is largely a personal attack that makes no attempt to deal with Bloom’s arguments. Then they assert the irrelevance of Bloom’s bachelorhood and his conjecturally repressed homosexuality to the appraisal of those arguments. Thus, they conclude, the reviewer commits an abusive ad hominem fallacy.
But is the attack a fallacy in the sense defined in this article? Certainly, dismissal by the single word “inane” is an inadequate response to a serious argument from a distinguished political philosopher commenting on a significant aspect of contemporary popular culture. And the innuendo that Bloom’s critique may be motivated by repressed homosexual desire is offensive.[i] But the reviewer would commit a fallacy only if the personal attack was a piece of reasoning that Bloom’s critique was incorrect or his supporting arguments flawed. In fact, the attack comes after the dismissal of Bloom’s position, and on a fair reading is not intended to support that dismissal. It is gratuitous, but not a flawed piece of reasoning, and so not a fallacy.

Although it is rare for someone to use a personal attack as an explicit basis for finding the person’s reasoning deficient, the 18th century moral philosopher and economic theorist Adam Smith used such a personal attack in just that way, in the course of some lectures on rhetoric. Weinstein (2006) quotes the following remarks about the 3rd Earl of Shaftesbury:
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Shaftesbury himself, by what we can learn from his Letters, seems to have been of a very puny and weakly constitution, always either under some disorder or in dread of falling into one. Such a habit of body is very much connected, nay almost continually attended by, a cast of mind in a good measure similar. Abstract reasoning and deep searches are too fatiguing for persons of this delicate frame. Their feableness of body as well as mind hinders them from engaging in the pursuits which generally engross the common sort of men. Love and Ambition are too violent in their emotions to find ground to work upon in such frames; where the passions are not very strong. The weakness of their appetites and passions hinders them from being carried away in the ordinary manner …”

Smith’s negative comments on Shaftesbury’s “cast of mind” differ from the personal attacks previously quoted as examples of the abusive ad hominem, in that they are not a response to a particular argument or piece of reasoning but to an entire corpus. Smith invites his audience to infer that they will not find in Shaftesbury’s writings abstract reasoning or the results of deep searches. Such an argument is in principle legitimate; everything depends on whether Smith is correct in inferring from Shaftesbury’s letters that he had a puny and weakly physical constitution, and from the puny and weakly physical constitution a puny and weakly “cast of mind” for which “abstract reasoning and deep searches” would be too tiring. The latter inference seems highly speculative, to say the least; a contemporary counter-example is the theoretical physicist Stephen Hawking, who has produced very deep abstract thinking about the nature of the universe despite the severe physical handicap of being a quadriplegic suffering from amyotrophic lateral sclerosis. Thus Smith’s reasoning is probably inadequate. But it cannot be dismissed on the ground that any attack on a person is in principle irrelevant to the quality of that person’s arguments.

Thus the sort of personal attack labelled as an abusive ad hominem does in fact occur with some frequency. It may have various functions. It can be a relevant attack on some aspect of an opponent’s ethos that bears on the acceptability of her position. It can be purely diversionary, an attempt to divert attention from the substantive claim or argument of one’s opponent. In the latter case, it is generally objectionable as a rhetorical strategy, but is not a kind of reasoning, and so not a mistake in reasoning. Hence, on the conception of fallacy with which we are working, it is not a fallacy. Rarely, as in the lecture by Adam Smith, it reasons explicitly from some deficiency in a person’s makeup to the general inadequacy of the person’s reasoning. But real cases of the abusive ad hominem do not make the crude mistake of reasoning from some fault of character or behaviour in an opponent to the unacceptability of some particular statement or argument by that opponent. Nor would addressees be deceived by such a crude mistake.

4. The Circumstantial Ad Hominem
The circumstantial ad hominem described in contemporary textbooks is in effect a specific version of the abusive ad hominem, namely, an allegation that the opponent is predisposed to take a certain position and to argue for it, because of self-interest or dogmatic bias (see for example Hurley 2003, p. 119). The textbooks typically interpret such allegations as arguments that the opponent’s argument is bad (Copi & Cohen 2002:145, Hurley 2003: 119). I shall consider with reference to two examples of allegations of self-interested bias whether this analysis is fair.

First example: The previously quoted letter from the executive vice-president of the Fur Council of Canada prompted the following reply:
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Whatever Brigitte Bardot’s ethical failings in the minds of some, such as Alan Herscovici of the Fur Council of Canada (Bardot’s Blind Spots-letter March 24), the annual slaughter of baby seals off Canada’s east coast is a bloody stain on our national identity. The majority of Canadians are appalled by this massacre and, like Ms. Bardot, want it to end. Of course, Mr. Hercovici’s objection to Ms. Bardot’s crusade can only spring from his own pure conscience. One would never accuse him of supporting this ecocide just to protect the profits of the vanity industry. (G. Cooper, Toronto, The Globe and Mail, 25 March 2006)

The first paragraph of this letter asserts the writer’s opposition to the annual seal hunt, regardless of the ethical failings pointed out by the fur industry official, on the ground that it is “bloody” and a “massacre”. The second paragraph ratchets up the emotive language by calling the hunt an “ecocide”, and uses irony to point out that the fur industry has a vested interest in continuing the hunt. The reader is expected to infer that the official’s letter is motivated by this financial interest, which the writer’s use of the expression “vanity industry” implies is illegitimate. Thus this part of the letter is clearly a circumstantial ad hominem, in the sense of an allegation that the fur official’s attack on Bardot’s credentials is motivated by a vested interest rather than by a “pure conscience”. Its point is clearly not to show that he was mistaken in what he wrote about Bardot, as textbook accounts of the circumstantial ad hominem would have it, but to undermine his credentials in somewhat the same fashion as he undermined Bardot’s. As such, it makes a perfectly legitimate point. Further, although the writer uses overheated and unsupported emotive language rather than reasoned argument to condemn the seal hunt, the writer does assert opposition to it independently of the circumstantial ad hominem attack, and does not use the official’s bias as an irrelevant reason for thinking that the seal hunt should be abolished. There is no fallacy of irrelevance in the letter.

Second example: The following sentence was displayed on a screen as part of a presentation in August 2005 on global climate change:
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Almost all criticisms of global climate predictions are backed by people with much to lose if policies are changed. (Howard Barker, Cloud Physics Research Division, Meteorological Service of Canada, “The real scoop behind global climate change”, presentation at the Hamilton Spectator auditorium, Hamilton, Canada, 11 August 2005)

Asked in the question period what conclusion he wanted the audience to draw from this point, the author replied: “They are not motivated by a scientific interest in the truth.” In subsequent e-mail correspondence, I suggested to him that this sort of circumstantial ad hominem is typically intended as a warning that the opponent’s argument should be scrutinized very carefully. He responded: “Exactly! That was the point I wanted to get across to the audience, and that is why I stated explicitly that they should note the affiliation of an author as well as the quality of the citations provided.”
Attention to “the affiliation of an author” is a perfectly legitimate critical response to a person’s statements or arguments. It can legitimately put one on one’s guard. Although it would be a mistake to use an allegation of bias as a proof that a position is incorrect or an argument is flawed, real allegations of bias are not fairly interpreted as committing it. The circumstantial ad hominem, understood as an allegation of bias, therefore does not belong in a list of logical fallacies.

5. Summary
If we accept Trudy Govier’s articulation of the traditional conception of a fallacy as “a mistake in reasoning, a mistake which occurs with some frequency in real arguments and which is characteristically deceptive”, there is no argumentum ad hominem fallacy. In its original meaning, an argumentum ad hominem is a perfectly legitimate dialectical argument from the concessions or commitments of an opponent that one need not share. The tu quoque historically emerged from this sense as an appeal to commitments implicit in the behaviour of one’s critic; it legitimately challenges the critic to explain away an apparent inconsistency between word and deed. The purely abusive ad hominem is generally either a relevant attack on the opponent’s ethos in a rhetorical context or a diversionary tactic that does not involve reasoning, and so is not a mistake in reasoning. The rare variant found in Adam Smith’s lecture, quoted above, is a general attempt to infer limited reasoning capacity from some other deficiency; such a pattern of reasoning is not in principle mistaken, although particular examples of it may make unwarranted assumptions. The circumstantial ad hominem attributes the position of one’s opponent to self-interest or a dogmatic bias, and thus raises legitimate suspicion about the credibility of the opponent’s statements and arguments.

NOTE
[i] In fact, as Saul Bellow makes clear in his 1999 roman à clef Ravelstein, Bloom was a homosexual, who did not publicly announce the fact but made no attempt to hide it from his friends. He was not repressing his homosexuality.

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