Tu Quoque

Description:

The argument tries to defend a position by showing that its shortcomings are shared by the opposing position. In effect, the argument say, "My position may be bad, but you should accept it because my opponent's position is just as bad."

Comments:

The phrase "tu quoque" is a Latin phrase meaning "you also." I suppose it was the Latin form of such juvenile taunts as "You're one, too!" or "It takes one to know one!" or the schoolyard chant, "I am rubber, you are glue. What bounces off me sticks to you." There is a version of the Tu Quoque fallacy that is hard to distinguish from the Secundum Quid fallacy, namely, "My opponent broke the rules, so I am allowed to do so, too." The (very subtle) difference may be this: if I try to defend my breaking of the rules on the grounds that my opponent did it first, that is Tu Quoque; if I argue that anyone may break the rules on the grounds that someone did, that is Secundum Quid.

Examples:

"Creationism is sometimes accused of being unscientific - of being merely a matter of faith - but, the Theory of Evolution is also just based on faith."

"The Republicans are accusing the president of refusing to negotiate. Well, they had their chance. Six months ago we offered to negotiate, and they turned us down flat."

"No puppet! No puppet! You're the puppet." - Donald Trump, Oct. 20, 2016, during the presidential debates in reply to a statement by Hillary Clinton implying that Trump was a puppet of the Russian government.

Discussion:

A fundamental principle of reasoning in ethics, in terms that even children instinctively understand, is "turnabout is fair play." Any rule that applies to one person must be applied to all, or at least to all other persons in relevantly similar circumstances. This symmetry of moral agents to each other is what underlies such fundamental moral principles as the Golden Rule or Kant's Categorical Imperative. Fair play in argumentation is, of course, just one place in which the general "turnabout" principle is applied with legitimate and appropriate force. If one reasoner is entitled to use a particular form of reasoning, a particular sort of appeal, or a particular background assumption, then all other reasoners in the discussion are entitled to use it as well

The Tu Quoque fallacy mimics the legitimate use of the principle of ethical symmetry. However, an error is introduced. It is fair to say that if one reasoner is not entitled to use a particular appeal, then no other reasoner may use it either, but it does not follow from this that if one reasoner uses an illegitimate appeal (and is allowed to get away with it) that the appeal then becomes legitimate. Cheating does not become fair play merely because someone else cheats first. Fair play requires that no one cheat.

I had assumed that the Tu Quoque fallacy could only be used in cases in which the opponent was actually guilty of the same error as the person using the Tu Quoque argument. However, Donald Trump has repeatedly shown that this is not necessary. When accused of being mentally unstable he began (without evidence) calling his opponents unstable; when accused of being corrupt he began (again without evidence) calling his opponents corrupt. This proves that an irrelevant argument does not have to be true to be irrelevant; however, it would remain irrelevant, even if it were true.

Source: According to the Oxford English Dictionary, the earliest use of the phrase "tu quoque" to identify a fallacious style of reasoning is Sir Edward Bulwer-Lytton, in his 1838 novel Alice. Prior to that, the phrase was frequently used, not to name the fallacy, but to perpetrate the very fallacy so named. The fallacy also appears in Morris Engel, With Good Reason (1st ed. 1976).

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