Let’s face it, nobody likes to be insulted, but this very thing may be used as a form of argument in more or less subtle ways, a logical fallacy of irrelevance known by the Latin, because yours truly feels like being a pedant, the Argumentum ad Hominem, or the Argument to the Person.
This tactic of argumentation is the counterpoint to the Argument from Authority, a sort of polar opposite to it on the spectrum of genetic fallacies – arguments that focus on the source of a claim rather than valid logic or evidence – and like it attempts to call attention to real or imagined characteristics or origin of the subject in order to sidestep the argument being made, in this case those that are negative or unfavorable.
A special case of this is a subset called Poisoning the Well, also referred to as the Circumstantial ad Hominem, made even before the opponent makes his argument. This form associates the target with someone or something that is widely regarded as unpleasant or evil, such as implying or stating a connection with, for example, Nazis, terrorists, or an infamous serial killer.
The name of this subset probably derives from medieval Europe, when rumors abounded during outbreaks of plague that Jews were causing Christians to die from the epidemic by poisoning the local well-water, since the real vectors of the plague were unknown at the time. This differs from the usual form in that it can be made against both a person and an idea or belief.
In that hideous little abomination of a movie, Expelled, there was much use of this fallacy in the association of evolution and science in general with the Holocaust and the Nazis in particular.
The most common and least subtle form of this argument, used by the unimaginative, is the use of plain and simple verbal abuse to call attention to perceived (real or imaginary) shortcomings as a cheap way to dismiss an argument by dismissing the person making it.
“Your argument is wrong because you’re a known religious fundamentalist.”
“I don’t have to listen to you because you’re one of those Godless atheists.”
…or my favorite,
“I don’t have to provide any references for what I said. You should just accept it as I said it, or you are an obstinate fool for questioning something so self-evidently true.”
Often used is an alleged conflict of interest, bias, or personal prejudice, the Bias ad Hominem, indicating that the one this is used on is untrustworthy as an impartial source, or as is often the case of an American politician accusing his opponent of being a socialist or a fascist even when these claims are not only irrelevant but false.
Another is when critics of the modern anti-vaccination movement are implicated as paid shills in the pocket of the ‘Big Pharma’ conspiracy, and whose statements therefore must be taken with evil intent in mind.
Another is when mainstream scientists are accused of being afraid for their funding, careers, alleged political agendas, and reputations and so ignore or hide ‘the truth’ of the paranormal or global cooling. These last two, by the way, are also referred to as an argument from conspiracy, or an appeal to motive, another version of the bias ad hominem.
But the Ad Hominem argument is not always a fallacy, and in the proper use it may be a valid and effective form of argument when it is used to promote the goal of critical discussion rather than to obstruct it.
For example, a reasonable use is in pointing out a likely conflict of interest regarding the personal testimony of a claimant when the subject’s questionable background, credibility and circumstances are also true, relevant, and kept in their proper context — such as a disgruntled ex-gang member testifying in a criminal case when he has been given leniency or other favors for his testimony.
And this fallacy is more complex than one might think…
Less commonly known, and just as poisonous to an argument, is the positive ad hominem, which uses the same sort of reasoning, substituting alleged personal attributes, associations, or circumstances for relevant evidence in an argument, but this time uses positive traits, such as sincerity, kindness, or piety, though any virtuous trait will do, and here it shades into an argument from authority/appeal to virtue.
(Last Update 2014/04/04, Updated Text, Related Articles Links Added)