When and how to use them, and how to defend against them.

In rhetoric, an ad hominem (“to the man”) is an attack, not on the argument itself, but on the person making it. It is, in simpler words, an attempt to shoot the messenger.

When Winston Churchill called Mahatma Gandhi “a seditious Middle Temple lawyer now posing as a fakir,” he was attempting to undermine Gandhi’s character, or ethos.

Ad hominem, which is essentially an attack on a speaker’s ethos, is older than the books. It was not beneath Churchill, or even the Roman orator Cicero, who used it often, and went so far as to call Piso, Julius Caesar’s father-in-law, a “most foul and inhuman monster” (inhumanissimum ac foedissimum monstrum).

The first and most famous line of the most famous speech in all of Latin literature, Cicero’s First Catilinarian, is no more than an extended ad hominem:

When, O Catiline, do you mean to cease abusing our patience? How long is that madness of yours still to mock us? When is there to be an end to that unbridled audacity of yours, swaggering about as it does now?

When and how to use ad hominem

In academic circles, the ad hominem is regarded as a logical fallacy and frowned upon. It is uncivil, it stifles debate, and it is a tacit admission that you are losing the argument. It is forbidden in formal debates, and there has been a petition to ban it from the U.K.’s House of Commons.

But in rhetoric, anything goes, and an ad hominem can be legitimate if it serves to undermine the ethos, or pro hominem claims, of your opponents.

Even so, when attacking an opponent, it is better to put one’s words into the mouth of some third person, or to use paralipsis (mentioning something by saying that you will not mention it), as Cicero did in his speech Pro Caelio:

Clodia, I am not thinking now of the wrongs you have done me. I am putting to one side the memory of my humiliation. I pass over your cruel treatment of my family when I was away. Consider that nothing I have said has been said against you.

While debating Ron DeSantis, former Florida gubernatorial candidate Andrew Gillum succeeded in doing both at the same time, to great effect:

I’m not calling Mr. DeSantis a racist; I’m simply saying the racists believe he is a racist.

Such is the power of rhetoric that, had it not been for this single sentence, I may never have heard of Andrew Gillum. Often, when all is said and done, all that remains of a life is one or two sententiae, if even that.

How to defend against ad hominem

If you find yourself on the receiving end of an ad hominem, you can respond in one of four ways:

1. Ignore it.
2. Call it out as an ad hominem, e.g. “Instead of attacking me, could you please return to the argument, which you seem afraid of losing.”
3. Own it.
4. Bite back with an ad hominem of your own.

Which strategy to use depends on the context and the available material (so always do your research). But in the absence of a killer riposte, it is best and easiest to ignore the insult while looking slightly dismayed.

Finally, if returning an ad hominem, consider accompanying or accenting it with some gesture—the rhetorical device known as mycterismus. If the audience laughs, which it probably will, your opponent will not recover from it.

Neel Burton is author of the newly published How to Think Like Plato and Speak Like Cicero.