Definition
Ad Hominem
An ad hominem is an informal fallacy in which an argument is rebutted by attacking the person making it, rather than the argument itself.
The Latin phrase means “to the person”.
Why it Fails
The truth or falsity of a claim does not depend on who asserts it. An argument stands or falls on its own merits. Attacking the speaker’s character, motives, or circumstances leaves the original argument unaddressed.
Common Forms
Abusive
The speaker’s character is attacked directly.
“You cannot trust her view on tax policy; she has been arrested before.”
Circumstantial
The speaker’s circumstances are used to discredit the argument.
“Of course he supports the factory; he works there.”
Tu Quoque
The speaker is accused of hypocrisy.
“You cannot criticise my lateness; you were late last week.”
Example
Example
“Dr. Smith’s climate research is flawed because he drives a petrol car.”
The criticism concerns Dr. Smith’s behaviour, not the evidence or reasoning in the research. Even if the premise about his car is true, it does not establish that the research is flawed.