One of the stock rules of comment-enabled blogs, on-line newspapers and on-line forum decorum is the prohibition against personal attacks. It’s easy to police too. Any fool can moderate name calling: “you’re a bigot,” “you’re an arsehole,” or the ever popular command to go fellate yourself is easy enough to flag. But the root of all evil in forum—indeed the poison in the soul of internet discourse—is not bad words or telling people off. It’s arguing by imputing motivations, otherwise known as ad hominem argument.
Often the two ideas are taken to be interchangeable, but they’re not. Attacking someone by name-calling or shooting at them with all caps is not ad hominem. Ad hominem occurs when you reduce someone’s argument to undisclosed motives—motives that you’ve inputted to the person. “You’re only saying that because you’re a…/you believe…/you’re [insert emotional state, e.g., envious]” are the less subtle forms of this common strategy.
More subtle variations are no less ad hominem for it—nor are they any less destructive. “It’s pretty obvious that you don’t like so-and-so,” for example, is a subtle way to introduce an ad hominem argument. You’re saying, in effect, that the person is only criticizing so-and-so because he doesn’t like him, which is a way of evading the substance of the argument. Whether the person making the argument likes the person being criticised is immaterial.
A special variation of the last kind is that employed by all self-professed “positive” people who “don’t like all the negativity out there.” They’ll call anyone that disagrees with them a naysayer, and they’ll proclaim how they don’t listen to or otherwise suffer “negative energy.”
A subtler strategy still is to claim one’s opponent has a different motivation than the one he claims to have—not a bad one, necessarily, but one that’s easier to dispute. This type of ad hominem is a form of misdirection. It works too: so much so that some academics turn it into an all-purpose strategy for confronting any kind of opposition. Someone criticises your interpretation of history? No problem. Claim the critic has been flogging his own personal hobbyhorse for years. The ad hominem will be some variation on, “As for Smith’s criticism, he pushes his unpopular theory any chance he gets” or “Smith doesn’t like any theory that seems to support a [insert –ism] view of things.”
Arguing by motivations is also very seductive. For one, motivation is the backbone of a character. It’s also how we operate socially. Understanding someone motivation for asking a question, for example, determines how we answer it. Our perceptions of others determine how we interpret what they say. We interpret the same medical advice in different ways, for example, depending on whether we believe the physician is crooked or not.
Not all ad hominem arguments are fallacious, however. Socrates often makes what appear to be ad hominem arguments against his interlocutors in Plato’s dialogues. Yet the kind of arguments he makes show his opponents are speaking against their own stated convictions. That’s the key difference. He doesn’t impute motives to them. He elicits contradictory statements to expose his interlocutors’ own internal inconsistencies.