Ad Hominem Arguments


Traditional dictionary definitions on this topic are often imprecise as well as dated. Thus, I have been once again thinking about the long standing confusion over the terminology surrounding the ad hominem argument. Is an argument which the thrust is directed, not at a conclusion, but at some person who defends that conclusion, argumentum ad hominem only when fallacious?  The body of knowledge on this topic has evolved considerably in recent years but there still remains some disagreement which causes confusion over this question. Based on current perspectives, I would like to propose a framework to simplify the definition and understanding of the ad hominem argument for the lay person.


Always Fallacious?


In chapter 4 of the eleventh edition of Introduction to Logic by Copi and Cohen under the discussion of argument ad hominem it states:


"The phrase ad hominem translates into 'against the person.' It names a fallacious attack in which the thrust is directed, not at the conclusion, but at the person who asserts or defends it. This fallacy has two major forms, because there are two major ways in which the attack can be personalized."


"In legal proceedings it is sometimes appropriate to exhibit the unreliability of the person giving testimony to 'impeach the witness.' If dishonesty in other matters can be shown and credibility thus undermined, such impeachment, in that context, may not be fallacious. But it is never enough simply to assert that the witness lied; a pattern of dishonesty or duplicity must be exhibited, or inconsistencies with past testimony revealed. And even in this special context, the attack on the character cannot establish the falsehood of the testimony given; that inference would be fallacious" (Copi 2002).


By the above definition an ad hominem argument is viewed as a fallacious attack. When it is used in legal proceedings, where it may not be fallacious, the argument could no longer be categorized as ad hominem but only as a personal attack or inductive argument. In other words an ad hominem argument is always a fallacious attack.


Terminological Revisionism


It is understood that traditionally the ad hominem argument was classified in logic as a fallacy (Hamblin 1970), but recent research was showing more and more that ad hominem arguments can often be reasonable, and in many instances are not fallacious at all (Walton 1995).


In Douglas Walton's Ad Hominem Arguments he states “One of the most important aspects of this new and more advanced treatment of the ad hominem argument is the clarification of the terminological confusion in defining the ad hominem that has plagued this subject since the eighteenth century“ (Walton, 1998).


“Although the ad hominem argument is part of the introductory logic curriculum, included under the heading of fallacies in most modern introductory logic textbooks that have a section or more on common fallacies, the textbook treatments are not very helpful. Not only do they disagree on basic terminology and on fundamental questions of how to evaluate the ad hominem argument, as indicated above, but also they contain a central ambiguity on how to define this type of argument” (Walton, 1998).


“What emerges most significantly and clearly is the thesis that the argumentum ad hominem, in all three of its main types, is not an inherently fallacious scheme of argumentation in itself” (Walton, 1998).


“Although the personal attack or ad hominem type of argument has long been held to be fallacious in logic, the study of legal argumentation makes it abundantly clear that such arguments are by no means always fallacious. In many legal cases, they can be quite reasonable, and in fact they can provide the most important kind of evidence that is required to rationally assess the argumentation used in the case” (Walton, 2002).


“The appeal to expert opinion and the personal attack (ad hominem) types of argument are particularly important and common in legal argumentation, especially in witness testimony in a trial, as noted in Chapters 1 and 2. What is common to both these types of argument is that the evaluation of the strength of the argument depends crucially on an evaluation of the credibility of a source who backs up the premises of the argument” (Walton, 2002).


“In legal argumentation then, the ad hominem can be relevant under certain conditions. When it is relevant, it can be an extremely powerful way of attacking the credibility of a party, leading to a downward evaluation of the plausibility of that party's argument” (Walton, 2002).


According to Walton, an ad hominem argument is the use of personal attack by one party in order to try to refute another party's argument. The application of the ad hominem argument may be fallacious or not fallacious. An ad hominem argument that is irrelevant to the quality of the other party's argument may be considered fallacious. An ad hominem argument used in the case of testimony to assess ones argument may be considered relevant. 


By the above definition an ad hominem argument may be fallacious or not fallacious. The key to being fallacious is in the relevance of the attack. The term ad hominem argument is used in both cases.


Two Worlds Collide


In chapter 5 of the twelfth edition of Introduction to Logic by Copi and Cohen under the discussion of argument ad hominem, the perspective of a fallacious attack has softened:


"The phrase ad hominem translates into 'against the person.' An ad hominem argument is one in which the thrust is directed, not at a conclusion, but at some person who defends the conclusion in dispute. This personalized attack might be conducted in either of two different ways, for which reason we distinguish two major forms of the argument ad hominem: the abusive and the circumstantial."


“An important qualification is called for at this point. Ad hominem arguments are fallacious (and often unfair to the adversary) because an attack against some person is generally not relevant to the objective merits of the argument that person has put forward. However, there are some circumstances in which it is indeed reasonable to raise doubts about some conclusion by impeaching the testimony of one who makes a claim that would (if true) support the conclusion in question. In courtroom proceedings, for example, it is acceptable, and often effective, to call a jury's attention to the unreliability of a witness, and by so doing to undermine the claims upheld by the testimony of that witness. This may be done by exhibiting contradictions within the testimony given, showing that at least some of what has been asserted must be false. It may be done by showing (not merely asserting) that the witness lied -- an abusive but in this context appropriate counterargument. Testimony may also be undermined by exhibiting the great benefits that would accrue to the witness from the acceptance of his testimony, impeaching by circumstance. These are, strictly speaking, ad hominem considerations -- and yet they are not fallacious because of the special context in which those assertions are being put forward, and the agreed-upon rules for the evaluation of conflicting witnesses” (Copi 2005).


“But even in these special circumstances an attack upon the person of the witness does not establish the falsehood of what had been asserted. Revealing a pattern of past dishonesty or duplicity, or exhibiting an inconsistency with testimony earlier given, may cast justifiable doubt upon the reliability of the speaker, but the truth or falsity of the factual claim made can be established only with evidence that bears directly upon that claim, and not merely upon some person who denies or asserts it. In each case we must ask: is the attack upon the person relevant to the truth of what is at issue? When, as commonly, the attack is not at all relevant to the merits of the claim, the ad hominem argument is indeed fallacious” (Copi 2005).


Note an ad hominem argument is no longer defined as fallacious but is bifurcated into an ad hominem argument which is fallacious and ad hominem considerations which may not be. The key to differentiation is in the relevance of the attack. Ultimately if the attack is relevant we have ad hominem considerations which are not fallacious. If not relevant we have an abusive or circumstantial ad hominem argument.


As we can see both Copi’s and Walton's perspectives have narrowed to the point where they only differ on terminology. For both parties the entire issue of what is a fallacious attack is based on the concept of relevance. Unfortunately, the question remains unanswered on how exactly to determine relevance.


What’s the Matter with Relevance?


“An ad hominem argument, for example, could be a good argument, well supported by evidence, and meet all the (other) requirements of the argumentation scheme for ad hominem arguments, and yet it might still fail to be relevant. Evaluating an ad hominem argument requires, in addition to evaluating the particulars of the argumentation scheme as used in a given case, an evaluation of the relevance of the ad hominem argument in a context of dialogue. Hence it follows that the ad hominem fallacy is partly (but not exclusively, or in all cases) a failure of relevance. A comparable analysis can be given of the other appeals to emotion-the ad baculum, ad misericordiam, and ad populum arguments. When fallacious, these faults are partly fallacies of relevance, meaning that failure of relevance is one characteristic and important fault that makes them fallacious (in some cases). But it is not the only fault that can make them fallacious. In some cases, an ad hominem argument can be relevant, but still be fallacious. For example, in the legal type of case cited above, or in an election campaign, an attack on the person's character for veracity (say) could be relevant. Yet, in such a case, the personal attack could be so unwarranted by the evidence, and pursued with such a dogmatic and vicious zeal, that it could rightly be evaluated as fallacious. It could be fallacious because it interferes with the dialogue the participants are supposed to be engaged in, even though the ad hominem argument is relevant as used in this type of dialogue” (Walton, 2004).


Unfortunately even though Walton's excellent work on relevance in argumentation provides heuristics as well as examples on how to evaluate the relevance of an argument, it still is highly complex and difficult to decide exactly what is relevant – and even more difficult to prove.


Current Denotation


Bruce Waller represents a contemporary view in the latest edition of his Critical Thinking text where he states “Ad hominem arguments are, literally, arguments “to the person.” … The ad hominem fallacy is committed when one attempts to discredit an argument by attacking the source of the argument. But not all ad hominem arguments involve the ad hominem fallacy; in fact, most ad hominem arguments do not commit the ad hominem fallacy. (Many people regard all ad hominem arguments as automatically fallacious. That has the advantage of being easy; it has the disadvantage of being wrong.) An ad hominem argument commits the ad hominem fallacy only if it attacks the source of an argument and claims that because of some flaw in the source of the argument the argument itself is flawed” (Waller, 2005).


A Rose by Any Other Name?


Based on the above it is proposed that an ad hominem argument is one in which the thrust is directed, not at an argument, but at some person who defends the conclusion in dispute. Ad hominem arguments are fallacious when an attack against some person is not directed to the merits of the argument that the person has put forward. When we are dealing with expert witness, testimony, or opinion ad hominem arguments are not fallacious when they are used to dispute the credibility of a source that is the evidence for the conclusion or premises of an argument.


This ad hominem argument has the following form:

  • Person A makes factual claim X.
  • Person B makes an attack on person A.
  • Therefore A's claim is unwarranted.


It should be viewed that if the form of the argument is the same then the terminology used should be the same. Note that name-calling by itself is not an ad hominem argument. Rather, the attack on the arguer must occur as an ostensible attack on the arguers’ claim. The mere presence of a personal attack (such as sarcasm, personal abuse, or name-calling) does not indicate ad hominem: the attack must be used for the purpose of undermining the argument, otherwise the ad hominem argument isn't there. It is not a ad hominem argument to attack someone; the ad hominem argument comes from assuming that a personal attack is also necessarily an attack on that person's arguments. So all ad hominem arguments can be considered personal attacks but not all personal attacks can be considered ad hominem arguments.


It is important that one should assess an argument on its own merits, rather than on where it came from. However, when assessing someone's testimony:

  • Character, motivation, circumstance are relevant to assessing claims from testimony.
  • Logical inconsistency or practical inconsistency legitimately undermines someone's testimony: If they say both “A” and “not-A,” you can't rationally accept either claim based only on their testimony.


When dealing with testimony, as opposed to argument, one has to rely upon the credibility of the source. So, to the extent that claims have their source in testimony, criticism of the source of the testimony is logically legitimate.


Ockham’s Razor


In conclusion, it is suggested for the sake of simplicity that the ad hominem argument is fallacious except when used to dispute premises based on the opinion or testimony of others. One should use the term "ad hominem argument" to refer to any personal attack in the above argument form, fallacious or not.  "Ad hominem fallacy" should be reserved for fallacious ad hominem arguments. The important distinction is between argument and testimony: using a personal attack against an argument is fallacious, but using one against testimony is not. Some may feel this view is an over simplification but it can provide a straightforward way for the lay person to reference as well as understand personal attack arguments.


Today it appears there is much more agreement on the argumentum ad hominem then disagreement. Hopefully with continuing research those involved will not only describe the same activities but define them similarly. This represents a very minor clarification of terminology and I thank you very much for your consideration.





Copi, Irving M. 2002, Introduction to Logic 11th ed. New Jersey: Pearson Education, Inc.

Copi, Irving M. 2005, Introduction to Logic 12th ed. New Jersey: Pearson Education, Inc.

Hamblin, Charles L. 1970, Fallacies. London: Methuen.

Waller, Bruce N. 2005, Critical Thinking Fifth Edition. New Jersey: Pearson Education, Inc.

Walton, Douglas. 1995, A Pragmatic Theory of Fallacy. Tuscaloosa: University of Alabama Press.

Walton, Douglas. 1998, Ad Hominem Arguments. Tuscaloosa: University of Alabama Press.

Walton, Douglas. 2002, Legal Argumentation and Evidence. University Park: The Pennsylvania State University Press.

Walton, Douglas. 2004, Relevance in Argumentation. New Jersey: Lawrence Erlbaum Associates, Inc.




Abusive: expressing offensive reproach.


Argument: a unit of reasoning moving from premises that provides evidence to a conclusion.


Attack: to subject somebody to strong or vehement criticism or attempting to overthrow or bring into disrepute by criticism or satire.


Conclusion: decision based on or deduced from facts -- a decision made or an opinion formed after considering the relevant facts or evidence.


Expert: skilled or knowledgeable person: somebody with a great deal of knowledge about, or skill, training, or experience in, a particular field or activity.


Expert Witness: expert giving information to a court: an expert called to answer questions on the stand in a court of law in order to provide specialized information relevant to the case being tried. 


Name-Calling: verbal abuse, especially as a substitute for reasoned argument in a dispute.


Ockham’s Razor: is the philosophical and scientific rule that simple explanations should be preferred to more complicated ones, and that the explanation of a new phenomenon should be based on what is already known.


Opinion: personal view -- the view somebody takes about a certain issue, especially when it is based solely on personal judgment.


Personal: of, pertaining to, or coming as from a particular person.


Reproach: to find fault with; blame; censure.


Testimony: evidence that a person provides. It may take the form of a written or oral statement detailing what the person has seen or knows about a particular item. Testimony takes its strength entirely from its source.


Dictionary Definitions:


Traditional: ad hominem argument. For Aristotle, a *fallacy in which ‘persons direct their solutions against the man, not against his arguments’ (Sophistical Refutations, 178b17). Locke sees it as a ‘way to press a man with consequences drawn from his own principles or concessions’ (Essay Concerning Human Understanding, IV. xvii. 21). Locke’s ad hominem, though he does not describe it as a fallacy, is not a proof ‘drawn from any of the foundations of knowledge or probability’. *risus sophisticus.

[ Ted Honderich, The Oxford Companion to Philosophy Second Edition (New York: Oxford University Press, 2005) 7. ]




ad hominem. 1 (of an argument or reaction) arising from or appealing to the emotions and not reason or logic. attacking an opponent’s motives or character rather than the policy or position they maintain. 2 relating to or associated with a particular person. late 16th cent.: Latin, literally ‘to the person.’

[ Erin McKean, The New Oxford American Dictionary Second Edition (New York: Oxford University Press, 2005) 19. ]


Merriam-Webster’s Online Dictionary [ ]




A special thank you to Dr. Gary N. Curtis [ ] whose feedback has been incorporated in this text.