Ad hominem An ad hominem , short for argumentum ad hominem,
is a general category of fallacies in which a claim or argument is rejected on the basis
of some irrelevant fact about the author of or the person presenting the claim or argument.
Fallacious Ad hominem reasoning is normally categorized as an informal fallacy, more precisely
as a genetic fallacy, a subcategory of fallacies of irrelevance.
Ad hominem reasoning is not always fallacious, for example, when it relates to the credibility
of statements of fact.
Ad hominem arguments are the converse of appeals to authority, and may be used in response
to such appeals.
Ad hominem as it is discussed in this article refers to the logical fallacy argumentum ad
hominem, and not to the literal Latin phrase ad hominem.
Types Abusive
Abusive ad hominem usually involves attacking the traits of an opponent as a means to invalidate
their arguments.
Equating someone's character with the soundness of their argument is a logical fallacy.
Mere verbal abuse in the absence of an argument, however, is not ad hominem nor any kind of
logical fallacy.
Ad hominem abuse is not to be confused with slander or libel, which employ falsehoods
and are not necessarily leveled to undermine otherwise sound stands with character attacks.
Circumstantial Ad hominem circumstantial points out that
someone is in circumstances such that they are disposed to take a particular position.
Ad hominem circumstantial constitutes an attack on the bias of a source.
This is fallacious because a disposition to make a certain argument does not make the
argument false; this overlaps with the genetic fallacy (an argument that a claim is incorrect
due to its source).
The circumstantial fallacy applies only where the source taking a position is only making
a logical argument from premises that are generally accepted.
Where the source seeks to convince an audience of the truth of a premise by a claim of authority
or by personal observation, observation of their circumstances may reduce the evidentiary
weight of the claims, sometimes to zero.
Examples: Mandy Rice-Davies's famous testimony during
the Profumo Affair, "He would, wouldn't he?", is an example of a valid circumstantial argument.
Her point was that 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, in itself, carries little evidential weight against the claim of an affair.
Note, however, that this argument is valid only insofar as it devalues the denial; it
does not bolster the original claim.
To construe evidentiary invalidation of the denial as evidentiary validation of the original
claim is fallacious (on several different bases, including that of argumentum ad hominem);
however likely the man in question would be to deny an affair that did in fact happen,
he is no less likely to deny an affair that never happened.
Tu quoque Ad hominem tu quoque (literally: "You also")
refers to a claim that the source making the argument has spoken or acted in a way inconsistent
with the argument.
In particular, if Source A criticizes the actions of Source B, a tu quoque response
is that Source A has acted in the same way.
This argument is fallacious because it does not disprove the argument; if the premise
is true then Source A may be a hypocrite, but this does not make the statement less
credible from a logical perspective.
Indeed, Source A may be in a position to provide personal testimony to support the argument.
For example, a father may tell his son not to start smoking as he will regret it when
he is older, and the son may point out that his father is or was a smoker.
This does not alter the fact that his son may regret smoking when he is older.
Guilt by association Guilt by association can sometimes also be
a type of ad hominem fallacy if the argument attacks a source 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: Source S makes claim C.
Group G, which is currently viewed negatively by the recipient, also makes claim C.
Therefore, source S is viewed by the recipient of the claim as associated to the group G
and inherits how negatively viewed it is.
An example of this fallacy could be "My opponent for office just received an endorsement from
the Puppy Haters Association.
Is that the sort of person you would want to vote for?"
Other types of ad hominem reasoning When an ad hominem argument is made against
a statement, it is important to draw a distinction whether the statement in question was an argument
or a statement of fact (testimony).
In the latter case the issues of the credibility of the person making the statement may be
crucial.
Doug Walton, Canadian academic and author, has argued that ad hominem reasoning is not
always fallacious, and that in some instances, questions of personal conduct, character,
motives, etc., are legitimate and relevant to the issue, as when it directly involves
hypocrisy, or actions contradicting the subject's words.
The philosopher Charles Taylor has argued that ad hominem reasoning is essential to
understanding certain moral issues, and contrasts this sort of reasoning with the apodictic
reasoning of philosophical naturalism.