Argumentum Ad Hominem (i.e., Argument to the Person)

The ad hominem is probably the very first logical fallacy we ever used.

As toddlers we likely shouted a derogatory name at our parents, a sibling, or perhaps a young playmate in a moment of extreme frustration at not getting our way. It was the only thing we could thing of in our otherwise impotent situation. We wanted to send a message that we were unhappy and being young and unable to form a cogent argument, exploded with the best our young minds could muster at the time: “dumb-dumb!” In so doing, we committed our first logical fallacy.

That is the essence of the ad hominem fallacy. It is at its core a fallacy of irrelevance. In other words, it is a type of argument that even when true, doesn’t address the premise.  It is an attack of the person rather than of the position.  The argument bypasses substance and evidence and instead attacks characteristics of the opposition such as their appearance, personality, job, accent, race, age, and so on.

Sometimes the ad hominem is just old-fashioned playground name-calling.  Take the following fictional gun control debate:

Pro gun control: Guns kill people and need to be regulated.

Anti gun control: People kill people and gun ownership is a guaranteed right under the US Constitution.

Pro gun control: I would expect nothing less from a right-wing nut job.

Anti gun control: I would expect nothing less from a bed-wetting liberal.

And there it ends. Two ad hominem fallacies which have moved neither party closer to anything remotely resembling substance.

But ad hominem fallacies aren’t always as straightforward as playground name-calling. Sometimes attempts to discredit an argument by attacking the person presenting the argument are more nuanced and frankly more effective in that they subtly “link” the person to a position that implies bias.  It is a common trap, therefore it is incumbent upon the clever critical thinker to recognize when this tactic is employed.

Here is an example of this tactic from my own life. In this case, the ad hominem was intended to cast doubt on my proposition by attacking the circumstances of my job.  I was discussing the importance of vaccinations with what turned out to be an anti-vaxxer:

Me: Vaccines are highly effective at preventing many types of childhood diseases, such as measles, mumps, and whopping cough.

Anti-vaxxer: You worked at the Centers for Disease Control therefore you’re just regurgitating big pharma lies.

Me: My work at the CDC is irrelevant to my point.  I could be unemployed and that wouldn’t change the fact that scientific and medical evidence overwhelmingly illustrates the effectiveness of vaccines.

Anti-vaxxer: *promptly conceded and dashed out to get her child immunized*

If only the anti-vaccine argument ended that quickly and that successfully, but with poetic license, one can hope. That said, notice that rather than attacking my proposition by presenting evidence that would contradict it, the anti-vaxxer attacked my work history with the intention of casting doubt on my credibility – in this case by suggesting that my objectivity was compromised by my relationship with the CDC.

Also notice that part of the ad hominem in this case was actually true; that is, I did in fact work at the CDC.  As I stated in my retort however, the fact of my relationship to the CDC was irrelevant to my proposition.  After all, I understood the efficacy of childhood immunizations long before I started working at the CDC. What is relevant to my proposition with regards to the CDC, is published data regarding the public health successes of childhood immunizations, such as the data illustrated in the below graphic. But anti-vaxxers have no countervailing data to support their claims, therefore ad hominem is one of their only options.

Finally, not every charge of argumentum ad hominem is actually ad hominem.  Some people will claim they are victims of ad hominem arguments, when the arguments are in fact relevant.  This can be a particularly frustrating situation for someone trying to have an intellectually honest conversation. Take the following hypothetical example:

Person A: Did you see my Facebook post about those 2 million year old hominid fossils recently discovered in Ethiopia?

Person B: I don’t read those posts – they are lies concocted by science to trick us in to believing the earth is older than 6000 years.

Person A: Wow, I didn’t realize you were a young earth creationist.

Person B: No need for ad hominem attacks!

Person A: Wait….you actually are a young earth creationist correct? Why is that an ad hominem?

Person B: I just believe what my parents told me to believe.

Person A: But you’re just factually incorrect. In fact, ancient Mesopotamians had already invented beer by the time you think the earth was created.

Person B: More ad hominem!

Person A: Again, no. That’s a true statement based on archaeological discoveries in the region.

Our hypothetical discussion is going nowhere fast and while intended to illustrate Person B’s false claims of ad hominem arguments, also shows us a glimpse of someone who isn’t really interested in the evidence. They have accepted a conclusion in the absence of any evidence to support that conclusion.

A word of caution here. Labeling people who hold positions known to have no bearing in evidentiary reality, such as calling someone who doesn’t believe vaccines are effective an “anti-vaxxer,” or calling someone who believes a being created the earth 6,000 years ago a “creationist,” is unlikely to result in significant forward progress if that is one’s intended goal.  In other words, while these may not necessarily be ad hominem arguments, calling someone an anti-vaxxer or a creationist will do little to persuade them not to be anti-vaxxers or creationists.

Refrain from using ad hominem arguments and practice recognizing them so that you can, dare I say, inoculate yourself against them and the bad arguments they inspire!