Proverbs 4:24 “Put away perversity from your mouth; keep corrupt talk far from your lips.” Proverbs 6:2 “if you have been trapped by what you said, ensnared by the words of your mouth.” Proverbs 14:3 “A fool’s talk brings a rod to his back, but the lips of the wise protect them.” Proverbs 15:2 “The tongue of the wise commends knowledge, but the mouth of the fool gushes folly.”
“Tu Quoque” in Latin means “you too.” This is the type of argument that is used in dismissing someone’s viewpoint on an issue because he himself is inconsistent in that very thing. In other words, “you too.”
In this type of argument someone might come to another person and say that they should not do a particular thing (whatever it is) but the response from the person is: “But you do it too.” What the person is telling them not to do might be something very bad for them, but they do not listen because of the inconsistency of the other person telling them not to do it.
For example, an older person might come to a teenager and tell him/her not to smoke because of the bad health consequences of smoking. However, the teenager does not really listen because the older man himself is smoking. To think that way is to fall into fallacious thinking. Whether the person giving you the advice smokes or doesn’t is beside the point. The point is smoking is bad and it is bad for your health.
People who commit this fallacy often have guilty consciences, and it makes them feel better somehow when they shift their guilt onto someone else. This fallacy also happens when somebody claims that two wrongs make a right.
So the question is, why should we listen to someone who is not consistent with his or her own argument? There are two good reasons. First, we must always allow people to change their minds through experience.
When faced with such a challenge the famous economist John Maynard Keynes once put it quite nicely: “When I find out that I’ve been wrong, I change my mind – what do you do?”
The second reason is that we should not look at the credibility of the person offering his opinion, but the merits of the argument that he is making.
For example, the older man through experience understands what smoking really has done to his own health and this has caused him to form the opinion that he is giving to his younger friend. He has changed his mind about smoking. In other words: Smoking is bad.