An ad hominem 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 source 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.
Ad hominem argument is most commonly used to refer specifically to the ad hominem abusive, or argumentum ad personam, which consists of criticizing or attacking the person who proposed the argument (personal attack) in an attempt to discredit the argument. It is also used when an opponent is unable to find fault with an argument, yet for various reasons, the opponent disagrees with it.
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 source 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. 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 inverse of argumentum ad verecundiam, in which the arguer bases the truth value of an assertion on the authority, knowledge or position of the source asserting it. Hence, while an ad hominem argument may make an assertion less compelling, by showing that the source making the assertion does not have the authority, knowledge or position it claims, or has made mistaken assertions on similar topics in the past, it cannot provide an infallible counterargument.
An ad hominem fallacy is a genetic fallacy and red herring, and is most often (but not always) an appeal to emotion.
A (fallacious) ad hominem argument has the basic form:
Source A makes claim X
There is something objectionable about Source A
Therefore claim X is false
Let me repeat the money quote:
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 source making the inference.
I freely admit that I am a semi-civilized guy with a raunchy and politically incorrect sense of humor and that I’ve said things from time to time that were inappropriate. With Google and the obsessive focus of a blogstalker you can find some of them. But that doesn’t change the fact that I’m a flaming liberal and that when it matters my heart’s in the right place. It also doesn’t disprove anything I said about Obama or any of his cult followers.
Kreepy Kevin and the internet vermin that hang out with him can kiss my ass.
Where Blogstalkers come from:
Just so there is no misunderstanding, by “internet vermin” I am specifically including a certain two-faced, talentless bullshitter who scammed some people out of their money and then betrayed their trust. To that person I say:
FUCK YOU TOO