Ad Hominem
beginnerAttacking the person making an argument instead of addressing the argument itself.
Examples
"You're not a scientist, so your objection to this study is invalid."
"Let me address your specific objection to the methodology."
The person's credentials are irrelevant to whether their objection has logical merit. Arguments stand or fall on their own.
"Of course he supports tax cuts — he's rich."
"His argument for tax cuts relies on supply-side assumptions. Here's why those assumptions are questionable."
His wealth might explain his motivation, but it doesn't address whether his argument is sound.
"She's a hypocrite — she drives a car but argues for climate policy."
"Her personal choices are separate from whether the policy argument is logically sound."
Hypocrisy is a character flaw, not a logical refutation. A hypocrite can still make a valid argument.
Why It Matters
Ad hominem is the mirror image of appeal to authority. If appeal to authority accepts claims based on who makes them, ad hominem rejects claims based on who makes them. Both commit the same fundamental error: confusing the source of an argument with its logical content. This is why LogosLens teaches them together — understanding one helps you see the other.
The Core Error
Ad hominem attacks the person rather than the argument. The Latin literally means “to the person” — the response is directed at the speaker instead of what was said.
The structure:
- Person X makes argument A.
- Person X has characteristic C (bad character, bias, hypocrisy, lack of credentials).
- Therefore, argument A is false.
Step 3 doesn’t follow. The truth or falsity of an argument is independent of who makes it.
Three Common Forms
Abusive: Direct insult. “You’re an idiot, so your argument is wrong.” The least subtle form — most people can spot this.
Circumstantial: Pointing to the person’s circumstances. “You’re a tobacco executive, so your argument about smoking is biased.” The person’s circumstances may explain why they argue as they do, but they don’t determine whether the argument is valid.
Tu quoque (“you too”): Pointing to hypocrisy. “You smoke, so you can’t argue that smoking is harmful.” Hypocrisy is a moral failing, not a logical refutation. A doctor who smokes can still give medically sound advice about the dangers of smoking.
The Mirror of Appeal to Authority
Ad hominem and appeal to authority are two sides of the same coin:
- Appeal to authority: “Accept this because of who said it.”
- Ad hominem: “Reject this because of who said it.”
Both make the same category error: treating the identity of the speaker as relevant to the logical validity of the argument. Master one and you’ll see the other everywhere.