What is an ad hominem? What isn’t?

It seems as though, in pretty much every argument I’ve ever had, at some point or another someone mistakes what an “ad hominem attack” or the “ad hominem fallacy” really is. It’s a pretty easy way to score rhetorical points, shouting about your opponents using ad hominems when really they’re just insulting you, usually in parallel to making an argument. It’s less easy to score said rhetorical points when someone else in the conversation actually knows the difference and is willing to point that difference out. This post is intended to be a go-to reference any time someone makes this mistake, so please, by all means, link it whenever necessary.

The term “ad hominem” is Latin, meaning “to the man”. It indicates that your argument is directed at the person making it, rather than at the argument proper. Most of the time, it refers to insults, as with the following cases.

An ad hominem fallacy is constructed something like this.

Premise 1: You are an idiot. (Unstated premise 2: Idiots cannot argue worth a damn, and are always wrong.)
Conclusion: Therefore, your argument about X is incorrect.

A “mere insult” packaged in with an argument is constructed something like this:

Premise 1: Your argument X is incorrect and fails on such-and-such grounds if fact Y is true.
Premise 2: Fact Y is common knowledge, easily demonstrated, and/or has copious proof as to its truth.
Conclusion: Therefore, you are wrong about argument X (and also, you are an idiot).

As you can see, merely insulting someone does not rise to the level of an ad hominem attack or fallacy. One must make the insult as a PREMISE of the argument, rather than as part of the CONCLUSION.

Another formulation of the “mere insult” runs something like:

Premise 1: Your argument X is not true if the argument itself is nonsensical.
Premise 1a: If you are making an argument that is nonsensical, you are an idiot for making it
Premise 2: Argument X is nonsensical — it does not comport with laws of logic, grammar, or depends on verbal legerdemain rather than facts.
Conclusion: Therefore, argument X can be dismissed. Sub-conclusion: premise 1a holds true because premise 1 holds true.

In this construction, premise 1a can be cut right out without damaging the core of the argument. It is not a premise attempting to prove the stated conclusion, it is attempting to prove the sub-conclusion.

As Randomfactor points out in the comments below, there is another type of ad hominem attack, which does not involve insults but rather aspersions as to the motivations or ability of the person to make the argument. It also can be coupled with legitimate argumentation, but often isn’t. This is also often referred to as “poisoning the well/water”, as Ryan Dunlop states in the comments. It goes something like:

Premise 1: Only people in X group can argue about Y topic.
Premise 2: You are not in X group.
Conclusion: Therefore, your arguments have no merit.

There are some cases where such an argument is actually worth making — for instance, climate change denialists might offer alternative theories that attempt to explain the current warming trends the Earth is experiencing, but since they do not have the benefit of any experience in the field of climatology, their arguments are woefully uninformed. Such an argument might serve as a good indicator that the person involved does not have a thorough understanding of the topic they’re bloviating about, and their argument does not actually rise to the level of overturning any of the peer-reviewed research they are in the process of gainsaying. As an argument against a person, this type of ad hominem fails only if the arguments made by the target do not actually raise any significant questions among those who are demonstrably knowledgeable about the topic at hand. For instance, someone merely claiming CO2 concentration in the atmosphere does not act as a heat forcing, without accompanying evidence, can be dismissed out of hand with a mere “you’re not a climate scientist”. Someone actually demonstrating that CO2 does not block infrared radiation in the ways that we’ve understood for the past 150 years, on the other hand, might have something to their argument.

In other words, such ad hominems are acceptable in cases where a person provides specious or no evidence for their assertions, where the balance of evidence from all peer-reviewed science suggests the exact opposite of their assertions. In those cases, feel free to also call them an idiot.

Because it’s so easy to mistake an insult for an ad hominem attack, I’ve seen so many arguments devolve into premature victory laps based only on the arguer having psychologically manipulated their opponent into losing their cool first. Just because a person argues passionately, does not mean they are engaging in a logical fallacy, nor does it mean they have forfeited the rest of the argument made in a particular comment, much less forfeited the overall discussion.

All of this is not to say that rudeness itself is acceptable in every discourse — in some, being tactful will win you more points. In others, belittling your opponent is the correct course of action, when they’re making arguments with little or no grounding in reality. I personally have a tendency of ratcheting up the rudeness in direct correlation to how civilly my opponent presents their arguments — if you’re willing to be congenial and make an honest effort to argue your point without resorting to insults (no matter how clever or subtle you think they are), then I’m generally willing to do the same. If I’m in a particularly crotchety mood, I’ll throw out a few belittling barbs about a particular idea or group of ideas in my initial address, but once those are out of the way, then I’ll try to undertake arguing the ideas on their merit without resorting to name-calling of the people who attempt to defend them.

I can’t say I’m always successful at maintaining my composure, especially when others mistake my barbs about an idea for barbs about the people who hold that idea and start launching outright attacks. When people don’t understand that my insulting, say, Catholicism for being a polytheistic religion derived from Christianity designed to give cover to wide-scale abuses of the general populace, I’m not also insulting the general populace who happens to adhere to that particular faith. It generally saddens me when people assume that’s the case.

I hope this primer is useful in your discussions. Remember, folks, always formulate your arguments such that the idiocy of your opponent isn’t a premise in the core of your argument! Their idiocy should, by rights, go either in the conclusion or in a parallel argument.

To easily link this post, cut and paste the following into your comments:

Here's <a href=" difference between an insult and an ad hominem</a>. You're welcome!
What is an ad hominem? What isn’t?

22 thoughts on “What is an ad hominem? What isn’t?

  1. 2

    Aren’t there two kinds of ad-hominem? 1: You dress funny, therefore your argument is unsound. 2: You’re a butcher, you can’t honestly argue the case for veganism.

  2. 7

    I just wanted to clarify that ad hominem case 2 is also referred to as “poisoning the water.” One attacks another’s motivations in order to also attack their argument(s). At least, that’s how I usually read this second case of ad hominem in logic texts.

  3. 10

    Someone actually demonstrating that CO2 does not block ultraviolet radiation in the ways that we’ve understood for the past 150 years, on the other hand, might have something to their argument.

    I think you meant infrared.

    But yay for linkable logic lessons! I love a blog that lets me link to things and say “you are wrong because this.” Could you maybe start a new tag for “logic” or “debate” or “fallacies” or something?

  4. 11

    Robert: I did indeed, and will amend shortly. This is what you get when you graft in a whole new argument post-publication and publish it with less actual rereading.

    Not that my general post cycle involves a lot of drafts. Dirty secret: I generally reread posts only after hitting publish, then edit frantically. It’s a good possibility if you’re reading something immediately after I post it, that it’ll change within the first few minutes when I catch an obvious error.

    Except there are some that I’ll sit on for months and months, refining and refining, until I post it, and nobody comments. Lack of positive reinforcement makes me sad, so I don’t do that next time.

  5. 12

    Poisoning the well can also run (and this is the form I’m more familiar with for poisoning the well):

    Person X did/said Y stupid thing
    (not necessarily stated) Therefore, do not trust what X says about Z

  6. 13

    The worst mistaken accusation of an ad hominem was when one person said that people disagreeing on the interpretation of the bible suggests it is not clear. The opponent thought this was an ad hominem since it was an argument involving people. Needless to say it was very frustrating to read.

  7. 14

    Because it’s so easy to mistake an insult for an ad hominem attack, I’ve seen so many arguments devolve into premature victory laps based only on the arguer having psychologically manipulated their opponent into losing their cool first.


    I only invoke ad hominem when the insult is the only thing that has been offered. Even if the insult is part of the premise, I tend to simply attack the premise rather than to crow ad hominem.

    Here is one of the few examples where I actually pointed out the person was engaging in ad hominem. Because that was the only thing he said, no attempt at an argument whatsoever. Not even, “You have no dick, therefore you are wrong.” Simply, “You have no dick.” Nice.

  8. 15

    James: MRAs can get nasty. They don’t have facts, so they natter on about discredited studies and how studies that agree with women are obviously part of the gynocracy. When they are backed into a corner, they’re vicious like that. Not that there’s anything wrong with having no dick, but the idea that you’ve been castrated by women (making you… servile to them somehow?) is pretty much their last resort.

    There’s a jackass like that guy infecting Stephanie’s old blog on an article about Title 9, though it was approaching its two week lockout period so I suspect he thinks he’s “won” by getting the last gainsay in.

  9. 16

    Ooh, MRAs are the Moon Landing Hoaxers of today. One informed me in an elevatorgate conversation that the reason women get raped is because men’s voices have been silenced. Apparently, rape didn’t exist before evil feminism.

    Anyway, I think that every time someone starts to write the words ad hominem into a comment, Clippy should appear saying “it looks like you want to accuse someone of an ad hominem attack, please read this link first.” And then it should link here. 🙂

  10. 17

    I had always thought that an ad hominem argument was under the area of:
    “You know my opponent hasn’t stopped beating his wife: how can you possibly believe him about climate change”
    yes, I know that’s also a non sequitur. I hope I spelled that correctly.Please bear with me, at my age, I forget stuff.

  11. 18

    Some time ago I referred to the Pope as “Benny Ratzi.” A Catholic* claimed that using that name was “ad hominem (abusive).” I explained it wasn’t ad hominem, since I wasn’t rebutting an argument. There are the further points I wasn’t arguing with Herr Ratzinge, and my statement remained the same if I’d called him “His Holiness Pope Benedict XVI,” “Benny Ratzi,” or “the guy in a white dress.”

    Using the name “Benny Ratzi” was at most disrespectful. Personally I feel the guy who decided the prestige and dignity of the Catholic Church was more important than the welfare of children had forfeited any claim of respect.

    *My brother, actually.

  12. 19

    Mr. Thibeault, when you say, “One must make the insult as a PREMISE of the argument, rather than as part of the CONCLUSION”, that is actually true in all cases. Even the last example (in the post) given by Randomfactor is just another case of that. If you expand it properly, it is:

    Premise 1: In order to argue about Y topic, you need Z (which only people in group X have); OR you need to NOT have Z’ (which everyone EXCEPT people in group X has).
    Sub-conclusion 1: Therefore only people in X group can argue about Y topic.
    Premise 2: You are not in X group.
    Conclusion: Therefore, your arguments have no merit.

    If premise 1 is legitimate, as in the case where Y is “climate science”, X is “climate scientists” and Z is “professional knowledge of climate science”, then the argument is sound.

    But if premise 1 is ultimately just an insult, the argument is not sound. For example, if Y is “veganism”, X is “non-butchers” and Z is “to not be dealing with meat on a daily basis”, premise 1 is really just saying “if you deal with meat, you can’t talk about veganism”, which is absurd (working with meat does not make you ignorant of veganism), and really just a veiled statement of prejudice.

    So, ultimately, you can pretty much summarize the entire class of ad hominem fallacies as “having the insult in the premise” or “having the conclusion rely on a premise that is nothing more than an insult”.

  13. 21

    “ad hominem attack” or the “ad hominem fallacy”

    Should these be conflated? Couldn’t the first refer to a simple insult and only the second to a logical fallacy in argument?

  14. 22

    Indi@20: yes, and that’s excellent, but would scuttle half my post if I edited to take that into account. Good clarification, nonetheless.

    ChasCPeterson@21: they COULD refer to simple insult and logical fallacy respectively, but in actual argumentation, they often refer to the exact same thing. These are people who don’t know what an ad hominem is to begin with, you have to understand. In one way, I was just covering the search term spread by including both. In another, I’m making the point that the term abusers conflate it themselves.

Comments are closed.