It is a very common fallacy that I've seen in many circles - In the world of media and in everyday life. In some cases it doesn't feel like a fallacy, but seems to make a point in that particular context.

For instance, imagine someone who is obese (controversial subject; I know). This person goes on advising people about health issues not necessarily obesity related but health in general. If someone else makes the comment "You shouldn't take health advice from that fat man." it is tu quoque, right? Since the other person is indeed obese and not addressing his own issues, doesn't that make him a hypocrite? Does being a hypocrite invalidates the credibility of his advices? If that is the case then is it logically sound to say "You shouldn't take health advice from that hypocrite"?

What's really confusing to me is why these two statements are considered different, even if they saying the same thing (hypocrite = staying obese). So is this one of those fallacies that is somehow OK to make given the context is clear and consistent?

  • Since the other person is indeed obese and not addressing his own issues, doesn't that make him a hypocrite? No, you do not know why the person in question is overweight. There are lots of possible reasons for their weight other than deliberate poor diet, weak will or whatever other failing you think we should attribute to such an individual. Feb 25, 2015 at 11:10
  • @ConradTurner Your statement might be correct, but it doesn't have anything to do with whether tu quoque is fallacious. Feb 25, 2015 at 19:55
  • It's very fallacious! The statement "People should eat healthy foods" is as true coming from someone who's healthy as someone who's not. Feb 26, 2015 at 20:56

2 Answers 2


Informal fallacies are judgment calls about problems in the structure of an argument. Their applicability is often debatable. (Formal fallacies like affirming the consequent are different in that they show the actual invalidity of an argument).

The fallacy of tu quoque is to fallaciously deny an argument because the source of the argument does not follow their own advice. But whether it is fallacious to point out that they don't follow their own advice depends on an interesting problem that we see described as far back as Aristotle.

Aristotle talks about akrasia, which we often translate as weakness of the will. It refers to a problem in the "practical syllogism". The practical syllogism is the idea that if I know what I ought to do, then I will do it. It turns out we often fail despite appearing to have full knowledge of what we ought to do.

Giving advice about, say, weight is an example where it seems fully plausible that a person giving it may rightly know what they are talking about even if they fail to follow it. Or to put it another way, if the leading scientist on obesity also happens to be fat that does not make what he's saying fallacious. On the contrary, we'd be guilty of a tu quoque to dismiss his knowledge in that arena. There is something bizarre seeming about following his advice on that point, but it's not fallacious to do so.

Consider for instance another informal fallacy: argument from authority. If we listen to the world's leading expert on obesity and do something about our weight because she says it, then that's an argument from authority. But that doesn't mean it's fallacious to follow her advice. Why? Because informal fallacies require judgments about the relevancy of her expertise.

To sum up, informal fallacies are patterns that are generally errant due to a problematic feature. But that feature is not always problematic, and we have to make a judgment about whether it is or not.

I don't generally take weight loss advice from really fat people, because (all other things being equal) it is difficult to accept they are experts on how to accomplish weight loss. But there may be exceptional reasons that make it so it's not fallacious. Conversely, there are contexts where tu quoque is perfectly appropriate (e.g., imagine one smoker telling another that it's easy to quit when the other smoker can't quit themselves. It's perfectly appropriate proof that their claim is wrong that they themselves empirically invalidate it).


A fallacy is not a moral judgment, it is a technical judgment. A fallacy is just an argument where the conclusion doesn't have a valid logical relationship with the premises. A morally exemplary person can still commit a fallacy, and the worst person in the world could still have impeccable logic. In the same way, being a hypocrite doesn't make a person's arguments wrong --it merely means she isn't practicing what she preaches.

If an obese person lectures you about your drinking, and you reply "what about your eating?" that may be personally satisfying, but it doesn't invalidate any correct points he has made about your situation. No accidents of his person change the validity of his arguments --for better or for worse.

What if (to use a less loaded example) a friend you know to be habitually broke tries to sell you on a new investment? In this case you can make a strong argument that if the investment was good, your friend would already be rich, therefore the investment is probably not good --that is not a fallacy. On the other hand, if that same friend tells you to save more than you spend, it's still valid advice even if he himself isn't following it. The two situations are superficially similar, but they are not the same. (The force of most informal fallacies stems from the fact that they are easily confused with similar situations that do provide the basis for strong arguments.)

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