{{wiktionarypar|ad hominem}}
An '''''ad hominem''''' [[logical argument|argument]], also known as '''''argumentum ad hominem''''' ([[Latin]]: "argument to the man", "argument against the man") consists of replying to an argument or factual claim by attacking or appealing to a characteristic or belief of the [[person]] making the argument or claim, rather than by addressing the substance of the argument or producing [[evidence]] against the claim. The process of proving or disproving the claim is thereby subverted, and the ''argumentum ad hominem'' works to change the subject.
It is most commonly used to refer specifically to the ''ad hominem abusive'', or ''argumentum ad personam'', which consists of criticizing or [[personal attack|personally attacking]] an argument's proponent in an attempt to discredit that argument.
Other common subtypes of the ''ad hominem'' include the ''ad hominem circumstantial'', or ''ad hominem circumstantiae'', an attack which is directed at the circumstances or situation of the arguer; and the ''ad hominem tu quoque'', which objects to an argument by characterizing the arguer as acting or arguing in accordance with the view that he is arguing against.
''Ad hominem'' arguments are always invalid in [[syllogistic]] logic, since the [[truth]] value of premises is taken as given, and the validity of a logical inference is independent of the person making the inference. However, ''ad hominem'' arguments are rarely presented as formal syllogisms, and their assessment lies in the domain of [[informal logic]] and the theory of evidence.<ref name="one">{{Cite web|url=http://plato.stanford.edu/entries/logic-informal/#One|title=Example: Ad Hominem|accessyear=2007|accessmonthday=September 10|publisher=Stanford Encyclopedia of Philosophy|year=1996|author=Stanford Encyclopedia of Philosophy|language=English}}</ref> The theory of evidence depends to a large degree on assessments of the credibility of [[witnesses]], including [[eyewitness]] evidence and [[expert witness]] evidence. Evidence that a purported eyewitness is unreliable, or has a motive for lying, or that a purported expert witness lacks the claimed expertise can play a major role in making judgements from evidence.
''Argumentum ad hominem'' is the converse of ''[[appeal to authority|argumentum ad verecundiam]]'', in which the arguer bases the truth value of an assertion on the authority, knowledge or position of the person asserting it. Hence, while an ''ad hominem'' argument may make an assertion less compelling, by showing that the person making the assertion does not have the authority, knowledge or position they claim, or has made mistaken assertions on similar topics in the past, it cannot provide an infallible counterargument.
The ''argumentum ad hominem'' is a [[genetic fallacy]] and [[red herring (fallacy)|red herring]], and is most often (but not always) an [[appeal to emotion]].
== ''Ad hominem'' as [[formal fallacy]] ==
A (fallacious) ad hominem argument has the basic form:
:Person A makes claim X
:There is something objectionable about Person A
:Therefore claim X is false
''Ad hominem'' is one of the best known of the logical fallacies usually enumerated in introductory [[logic]] and [[critical thinking]] textbooks. Both the fallacy itself, and accusations of having committed it, are often brandished in actual discourse (see also [[Argument from fallacy]]). As a technique of [[rhetoric]], it is powerful and used often because of the natural inclination of the human brain to recognize [[Pattern recognition (Physiological Psychology)|patterns]].{{Fact|date=April 2007}}
In contrast, an argument that instead relies (fallaciously) on the ''positive'' aspects of the person arguing the case is known as [[appeal to authority]].
[[Image:Eugenics ad hominem.svg]]
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The first [[premise (argument)|premise]] is called a 'factual claim' and is the pivot point of much debate. The [[main contention|contention]] is referred to as an 'inferential claim' and represents the reasoning process. There are two types of inferential claim, explicit and implicit. The fallacy does not represent a [[validity|valid]] form of reasoning because even if you accept both co-premises, that does not guarantee the truthfulness of the contention. This can also be thought of as the argument having an un-stated [[co-premise]].
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[[Image:Eugenics expanded ad hominem.jpg]]
In this example, the un-stated co-premise "''everything that A claims is false''" has been included, and the argument is therefore now a valid one. However in the ad hominem fallacy the [[inference objection|un-stated co-premise]] is always false, thereby maintaining the fallacy. Note that this does not imply that the contention "''eugenics is a bad idea''" is false, merely un-supported by the pattern of reasoning below it.
==Usage==
===In logic===
An ''ad hominem'' fallacy consists of asserting that someone's argument is wrong and/or he is wrong to argue at all ''purely'' because of something discreditable/not-authoritative about the person or those persons cited by him rather than addressing the soundness of the argument itself. The implication is that the person's argument and/or ability to argue correctly lacks authority. Merely insulting another person in the middle of otherwise rational discourse does not necessarily constitute an ad hominem fallacy (though it is not usually regarded as acceptable). It must be clear that the purpose of the characterization is to discredit the person offering the argument, and, specifically, to invite others to discount his arguments. In the past, the term ''ad hominem'' was sometimes used more literally, to describe an argument that was based on an individual, or to describe any personal attack. However, this is not how the meaning of the term is typically introduced in modern logic and rhetoric textbooks, and logicians and rhetoricians are in agreement that this use is incorrect.<ref name="two">{{Cite web|url=http://www.randi.org/jr/2007-02/020207geller.html#i3|title=Syvia Browne on the Ropes|accessyear=2007|accessmonthday=September 10|publisher=Swift - Weekly Newsletter of the James Randi Educational Foundation|year=2007|author=Swift |language=English}}</ref>
'''Example''':
:"You claim that this man is innocent, but you cannot be trusted since you are a criminal as well."
This argument would generally be accepted as reasonable, as regards personal evidence, on the premise that criminals are likely to lie to protect each other. On the other hand, it is an invalid example of ad hominem if the person making the claim is doing so on the basis of evidence independent of their own credibility.
In general, ''ad hominem'' criticism of evidence cannot prove the negative of the proposition being claimed:
'''Example''':
:"Paula says the umpire made the correct call, but this can't be true, because Paula was doing more important things than watching the game."
Assuming the premise is correct, Paula's evidence is valueless, but the umpire may nonetheless have made the right call.
'''Example'''
A ''[[reductio ad Hitlerum]]'' argument can be seen as a special case of an ''ad hominem'' argument, since these arguments are attacking something supposedly said or supported by [[Adolf Hitler]], who is usually considered to have been an evil person.
===Colloquially===
In common language, any personal attack, regardless of whether it is part of an argument, is often referred to as ''ad hominem''.<ref name="three">{{Cite web|url=http://www.bartleby.com/61/71/A0087100.html|title=ad hominem|accessyear=2007|accessmonthday=September 10|publisher=Bartleby.com|year=2007|author=Bartleby.com|language=English}}</ref>
== Types of ad hominems ==
Three traditionally identified varieties are '''''ad hominem abusive''''' (or ''ad personam''), '''''ad hominem'' circumstantial''', and '''''ad hominem tu quoque'''''.
===''Ad hominem'' abusive===
''Ad hominem'' abusive (also called ''argumentum ad personam'') usually and most notoriously involves [[insult]]ing or belittling one's opponent, but can also involve pointing out factual but ostensibly damning character flaws or actions which are irrelevant to the opponent's argument. This tactic is logically fallacious because insults and even true negative facts about the opponent's personal character have nothing to do with the logical merits of the opponent's arguments or assertions. This tactic is frequently employed as a [[propaganda]] tool among [[politician]]s who are attempting to influence the voter base in their favor through an [[appeal to emotion]] rather than by logical means, especially when their own position is logically weaker than their opponent's.
'''Examples:'''
* "You can't believe Jack when he says there is a [[God]] ''because'' he doesn't even have a job."
* "[[Charles Manson]] wrote this song, so it must be unlistenable".
* "Candidate Jane Jones' proposal X is ridiculous. She was caught cheating on her taxes in 2003."
===''Ad hominem'' circumstantial===
''Ad hominem'' circumstantial involves pointing out that someone is in circumstances such that he is disposed to take a particular position. Essentially, ''ad hominem'' circumstantial constitutes an attack on the bias of a person. The reason that this is fallacious in syllogistic logic is that pointing out that one's opponent is disposed to make a certain argument does not make the argument, from a logical point of view, any less credible; this overlaps with the [[genetic fallacy]] (an argument that a claim is incorrect due to its source).
On the other hand, where the person taking a position seeks to convince us by a claim of authority, or personal observation, observation of their circumstances may reduce the evidentiary weight of the claims, sometimes to zero.<ref name="four">{{Cite web|url=http://www.fallacyfiles.org/adhomine.html|title=Argumentum ad Hominem|accessyear=2007|accessmonthday=September 10|publisher=fallacyfiles.org|year=2007|author=fallacyfiles.org|language=English}}</ref>
'''Examples''':
* "Tobacco company representatives should not be believed when they say smoking doesn't seriously affect your health, because they're just defending their own multi-million-dollar financial interests."
* "He's physically addicted to nicotine. Of course he defends smoking!”
The [[Mandy Rice-Davies]] statement, "Well, he would [say that], wouldn't he?" is an example of a valid circumstantial argument. Her point is that since a man in a prominent position, accused of an affair with a callgirl, would deny the claim whether it was true or false, his denial carries no evidentiary weight.
===''Ad hominem tu quoque''===
{{main|tu quoque}}
''Ad hominem [[tu quoque]]'' refers to a claim that the person making the argument has spoken or acted in a way inconsistent with the argument. In particular, if person A criticises the actions of person B, a ''tu quoque'' response is that A has acted in the same way.
===Guilt by association===
{{main article|Association fallacy}}
Guilt by association can sometimes also be a type of ''ad hominem'' fallacy, if the argument attacks a person because of the similarity between the views of someone making an argument and other proponents of the argument.
This form of the argument is as follows:
:Person A makes claim P.
:Group B also make claim P.
:Therefore, person A is a member of group B.
Example:
:''"You say the gap between the rich and poor is unacceptable, but [[communists]] also say this, therefore you are a communist"''
This fallacy can also take another form:
:Person A makes claim P.
:Group B make claims P and Q
:Therefore, Person A makes claim Q.
Examples:
:''"You say the gap between the rich and poor is unacceptable, but [[communists]] also say this, and they believe in revolution. Thus, you believe in revolution."''
A similar tactic may be employed to encourage someone to renounce an opinion, or force them to choose between renouncing an opinion or admitting membership in a group. For example:
:"''You say the gap between the rich and poor is unacceptable. You don't really mean that, do you? Communists say the same thing. You're not a communist, are you''?"
Guilt by association may be combined with ''ad hominem'' abusive. For example:
:"''You say the gap between the rich and poor is unacceptable, but communists also say this, and therefore you are a communist. Communists are unlikeable, and therefore everything they say is false, and therefore everything you say is false.''"
==See also==
*[[Ad feminam]]
*"[[And you are lynching Negroes]]"
*[[Association fallacy]]
*[[Fair game (Scientology)]]
*[[Fundamental attribution error]]
*[[Shooting the messenger]]
==References==
{{Reflist}}
==Sources==
* {{cite book | last = Hurley | first = Patrick | authorlink = Patrick Hurley | title = A Concise Introduction to Logic, Seventh Edition | publisher = [[Wadsworth]], a division of [[Thompson Learning]] | date = 2000 | pages = 125-128, 182 | isbn = 0534520065 }}
* Copi, Irving M. and Cohen, Carl. Introduction to Logic (8th Ed.), p. 97-100.
==External links==
* [http://www.nizkor.org/features/fallacies/ad-hominem.html Nizkor.org: Fallacy: Ad Hominem].
* [http://www.nizkor.org/features/fallacies/circumstantial-ad-hominem.html Nizkor.org: Fallacy: Circumstantial Ad Hominem].
* [http://philosophy.lander.edu/logic/person.html Argumentum Ad Hominem]
* {{PDFlink|[http://io.uwinnipeg.ca/~walton/papers%20in%20pdf/04historical.pdf University of Winnipeg: Argumentation Schemes and Historical Origins of the Circumstantial Ad Hominen Argument]|70.2 [[Kibibyte|KiB]]<!-- application/pdf, 71948 bytes -->}}
* [http://atheism.about.com/library/FAQs/skepticism/blfaq_fall_adhominem_index.htm About.com: Argument Against the Person (Argumentum ad hominem)]
* [http://www.logicalfallacies.info/personalattack.html Logical Fallacies: Ad Hominem]
* [http://www.infidels.org/library/modern/mathew/logic.html#hominem Infidels.org: Logic and Fallacies: Constructing a Logical Argument (Argumentum ad Hominem)]
{{Red Herring Fallacy}}
[[Category:Genetic fallacies]]
[[Category:Logical fallacies]]
[[Category:Latin logical phrases]]
[[Category:Latin philosophical phrases]]
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