by Scott F. Aikin and Robert B. Talisse
Fallacies are improper inferences, popular ways of drawing conclusions from premises that in fact offer them no support. In its most common variety, ad hominem fallacy takes the following form:
Premise: Subject S is in some specified way vicious.
Conclusion: We should reject the things S says.
The vices identified in the premise of course vary. Depending on the context, it might be claimed that S is philanderer, a hypocrite, an alcoholic, a drug abuser, a child abuser, a racist, a pervert, a neoliberal, a lowbrow, an egghead, a neocon, a snob, a pinhead, a knownothing, and so on. To be sure, some of these traits may not be actual vices, but the effective deployment of the ad hominem depends only on the speaker's audience believing that the trait attributed in the premise is indeed vicious. The ad hominem's strategy is that of identifying the purported vice ascribed to S in the premise as sufficient grounds for rejecting the things S has said.
The prevalence of the ad hominem in political debate is easy to explain. Given the carefully curated and time-constrained forums in which most public political discourse occurs, it is just easier for disputants to talk about each other than the ideas and policies over which they disagree. Consequently, discussions of politics all too regularly become wranglings over personalities. Yet, despite its understandable prevalence, the garden-variety ad hominem is obviously fallacious.
What makes the ad hominem fallacious is that there is no stable connection between a vicious personality trait and the quality of view. Consider the alcoholism smear. Someone may say: Sam doesn't know enough about politics to be trusted – just look at how much she drinks! But there's nothing about being an alcoholic that precludes Sam from knowing a great deal about politics. (In fact, it might be that Sam drinks so much because she knows so much about politics!)
A purported vice needn't entail that the speaker is unreliable in the domain in question. And so, ad hominem arguments are fallacious in virtue of the fact that the vice ascribed in the premise is irrelevant to the conclusion about what the person has said.
But there's an additional respect in which the ad hominem is an instance of bad reasoning. The ad hominem is often deployed as a strategy for making disagreement emotionally taxing on one's interlocutor. That is, when one deploys an ad hominem, one imposes an additional burden on one's interlocutor. For now not only must she defend her view against your criticism, she must also bear the pressure of having her person subjected to scrutiny. For many, this makes debate too unpleasant, and so they learn to avoid critical exchange altogether. This has the consequence of granting the floor entirely to the verbal bullies. Insofar as argument and debate aim at goals like getting the truth, deepening understanding, and gaining a better grasp of the reasons and evidence relevant to an issue at hand, the impact of the ad hominem is decidedly anti-rational. It is an instance of purported reasoning that in fact undermines reasoning.
Now that we've identified the core of the ad hominem fallacy, it should be noted that not all cases of identification of an interlocutor's vice is argumentatively inappropriate. In the political context, many instances of name-calling are not deployments of the ad hominem. Political debate often aims directly at the evaluation of one's interlocutor's character. When Candidate A refers to Candidate B as a “snob,” she is typically not attempting to argue (ad hominem) that because B is a snob, B's statements are false. Rather, in calling Candidate B a snob, Candidate A is proposing an evaluation of B's character, and it's an evaluation that ascribes to B a character trait that can plausibly be expected to negatively impact B's judgment about public policy.
In a modern democracy, citizens must rely on the rationality and judgment of their representatives. Accordingly, representatives must be able to evaluate reasons, weigh evidence, and deliberate effectively. Clearly, some of the personal traits of our politicians are relevant when making judgments about their capacity to fulfill their duties. In political contexts, then, personal attacks may be deployed non-fallaciously. Indeed, in certain political contexts, personal attacks may not only be non-fallacious but also entirely appropriate and highly relevant. To repeat: in democratic politics, judgment matters, and the presence of certain character flaws is reliably correlated with flaws in judgment.
But this raises a difficulty. We noted above that the ad hominem involves two kinds of faulty reasoning. First, the ad hominem invokes an improper inference from an alleged character flaw to a negative assessment of what an interlocutor has said. Second, the ad hominem works strategically as a method for making debate increasingly uncomfortable, thereby ceding the field of political debate entirely to the bullies. We then suggested that political name-calling might not be fallacious, and even could be welcome; here, we pointed to the ways in which certain elements of a person's character are often correlated with features of their capacities for judgment. But doesn't the practice of political name-calling also serve to crowd-out those who haven't the stomach for receiving and giving insults? Doesn't a political environment where name-calling is prevalent also cede the field of politics to the bullies?
It may. But note that what distinguishes name-calling from the ad hominem is that only the latter involves an attempted inference from an alleged character flaw in one's interlocutor to the unreliability of something she has said. In order to avoid becoming a special case of the ad hominem, political name-calling must be seen as a criticism of one's interlocutor, the charge that one's interlocutor has insufficient judgment for his political role. This charge can of course be rebutted, and whoever introduces such a charge thus incurs the burden of showing how his interlocutor's alleged character flaw indeed infects his judgment. We might say, then, that political name-calling is non-fallacious only when it works as the beginning of a broader critique of one's interlocutor's capacities of judgment. Alternatively, when political name-calling is employed as a stand-alone smear tactic, it is indeed out of bounds.
To be sure, even this qualified defense of name-calling in political contexts leaves real-world politics a messy and largely disagreeable business. Even in a democracy – perhaps especially in a democracy – politics takes a strong stomach and a thick skin. Perhaps that's as it should be.