Tu Quoque

To what extent is a tu quoque argument a fallacy?

Let me explain.

Clearly in the narrow sense of a fallacy it is. An individual who responds to an accusation of immoral behavior by saying: "Well, you aren't so saintly yourself!" is not really responding to the original accusation. And her motive is probably less-than-kosher; she probably wants to distract attention from her moral turpitude.

But can we, with a few intermediate steps, turn this response into a coherent argument? For example, suppose the respondent continues: "Your unsaintliness is evidence of a social (or group) norm that permits such behavior. Thus, my behavior is congruent with the norms of our community."

One of my college professors had a useful distinction for this discussion. He used the term moral to refer to the extent to which a given behavior was consistent with the prevailing community norms. He used ethical to refer to the extent to which those community norms were good ones. (He claims this distinction is ubiquitous. I don't believe him.)

So we might be able to see the tu quoque response as logically coherent if we are content to stop our analysis at the moral character of a given behavior. To get to the ethical aspect of that behavior, however, the argument has to take one more (tenuous) leap: "And our community's norms are good ones."

But if you are a pragmatist, postmodernist, or moral relativist, you are probably quite content to stop before that last leap. So you might see tu quoque as a valid (though not necessarily desirable) form of argument.

Of course, there's a critical sample-size problem with using 2 individuals' behavior as evidence of a group norm. But it works in relationship fights!

Thoughts?