by Scott F. Aikin and Robert B. Talisse
Consider the following exchanges.
Hypocrite: A father advises his daughter not to smoke, since it is addictive and causes lung disease. However, the father himself is a heavy smoker. And the daughter cannot help but notice this and point out her father's hypocrisy. On this basis, she rejects her father's advice.
Waffler: A candidate for public office has spoken on some issue many times, but her articulated view has changed over that time. Years ago, she was a staunch critic of some policy, but now she has come to support it. Her opponent seizes on this and points out her waffling on the matter. He holds that her inconsistency indicates that she is unprincipled.
Tu Quoque arguments are ad hominem strategies of criticism wherein a speaker's conclusion is criticized on the basis of the fact that the speaker has a record of inconsistency with the conclusion. The tu quoque may take the form of charges of hypocrisy when someone affirms a practical proposal that she has regularly failed to follow. The tu quoque also can arise when a speaker has not consistently held or articulated the same view in the relevantly similar contexts; the charge of flip-flopping is hence a version of the tu quoque. Given that tu quoque arguments belong to the ad hominem family, it is commonly held that tu quoque arguments are intrinsically fallacious; they are thought to suffer from failures of relevance. The fact that someone is a hypocrite doesn't mean he's wrong, and that someone's views have changed doesn't mean she isn't well-informed or worth hearing.
We've discussed elsewhere (here and here) the ways in which relevance problems for certain versions of the tu quoque might be resolved. Sometimes, it is indeed relevant that someone is a hypocrite or has an inconsistent track record on an issue; those facts may show that the person is insincere or has ideas that are not practicable. However, there is yet a further form of tu quoque argument which, given the right circumstances, is not only relevant, but presents exactly the correct critical point.
Consider the following dialogue. Adam and Betty are discussing the relative merits of two plans of action, O and P. Adam prefers O, and Betty prefers P. Both realize that the two plans each have benefits and costs, and thus neither will be perfectly unproblematic. Call this a case of options weighing, and when one is doing this kind of weighing, one is keeps a pro-and-con list for each of the options. Once the lists are (reasonably) complete, one then weighs the options in light of the tradeoffs for each. This is a rough and ready model for pro tanto reasoning — we collect reasons for and against our views and plans, then we weigh our options.
Now imagine that in this critical dialogue, Betty points out that O — Adam's preferred plan — has some specific problem. Call it Problem X. That's a reason against O. But now imagine further that Adam's reply is that Betty's preferred plan, P, also confronts Problem X. Adam may exclaim: “You should talk, Betty. Your idea faces Problem X, too!”
Given the way the tu quoque is typically defined, Adam's reply is an instance. Betty has the same problem that she criticizes Adam for, namely Problem X. But notice: The fact that the problem is shared among both options is surely a relevant consideration in weighing the relative merits of O and P. In fact, it is not only relevant to the discussion, but making this observation is precisely what drives the pro tanto weighing of options. That is, if we want to have reasonably complete pro-and-con lists for each of our options, it is a salient fact that X is a problem for both. And it is important to say so!
When weighing the relative merits of options, tu quoque charges can be relevant. Thus the tu quoque is not always fallacious. Of course, oftentimes more is made of tu quoque challenges than they merit. So Adam may, after deploying the tu quoque, proceed as though he has defeated Betty's proposal. This would be obviously fallacious. Still, for Adam to show that both options must confront the same problem is nonetheless a relevant contribution to an options-weighing critical dialogue.
The lesson is a relatively simple one. Our most common textbook classes of informal fallacy — such as question-begging, hasty generalization, argument from ignorance, and so on — are really only heuristics for argument criticism and evaluation. They are not foolproof ways to undercut an argument, nor are they exceptionless forms that always instantiate flawed arguments. Rather, because informal logic allows for contexts and specific non-formal cases of relevance, the fallacy forms are more cases for reflection, occasions for asking critical questions. More generally put, the textbook informal fallacies are properly understood not as ways to defeat an opponent's argument, but rather as ways in which one can initiate argumentation over a proposed piece of reasoning.