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Because we have never had complaints about our food, our food must not be bad.

The restaurant owners always deny that the food is the reason customers are not returning and they justify that the food cannot be the reason for their lack of success because they have never received complaints.

  • First off welcome to philosophy.SE. Please look at meta.philosophy.stackexchange.com/questions/3040/… . – virmaior Nov 21 '15 at 1:29
  • This reminds me of an old Benny Hill joke: just because nobody complains doesn't mean parachutes never fail. – Bumble Jan 15 '16 at 13:18
  • The title gives a valid inference in classical logic known as contraposition, so it is not a fallacy. The problem is that the "if the food were bad the customers would complain" conditional is false, the customers may just stop coming instead. – Conifold Oct 27 '17 at 18:39
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First off, it's important to note that as understood in philosophy, fallacies apply to arguments. Thus, we have to make sure someone is making an argument. In the case of "Kitchen Nightmares", this seems at least somewhat justifiable.

Also, it's important to note that "name the fallacy" is normally not the most important thing to do with fallacious arguments. The argument is something like this:

  1. If the food were bad, then people would complain.
  2. No one complains.
  3. Therefore, the food is not bad.

This argument is formally valid. But the argument is not sound. Validity means if the premises were true, the conclusion must also be true. Soundness means validity and true premises.

Where then does this argument go wrong? I would say that it goes wrong in that we have no reason to believe the first premise is true. Thus, the argument appears to engage in what we can call a "false cause fallacy." But again, it's not important to name the fallacy so much as it is to show that an argument is wrong.

  • 3
    The second premise is also somehow dubious. – gnasher729 Nov 22 '15 at 16:22
  • 1
    Good point. There is possibly some equivocation going on between "complain generally" and "complain to me". – Jeff Y Jan 14 '16 at 23:19
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The logical rule that you quote is perfectly fine: If it is true that (if A then B), and it is true that (not B), then it is true that (not A). If it were true that bad food would always lead to complaints, and there were no complaints, then it would absolutely be true that the food must be good. No fallacy here.

There are two problems. First, the statement that there are no complaints might be made up, a lie. The restaurant owners seem to be in denial here. Just because the restaurant owners claim there are no complaints doesn't mean that is the truth. If a lot of food is returned then I somehow doubt that there are no complaints.

Second, it is not true that there will always be complaints when the food is bad. It is a very cultural thing. In some cultures, people will complain, either because they like complaining, or because they want to give the restaurant a chance to improve. In other cultures, this doesn't happen. People assume that it is impolite to complain. They just don't come back. You don't get complaints, you just get an empty restaurant. Depending on the attitude of the restaurant owner, they can easily stop people from complaining. Which is worse for business than customers complaining.

Summary: You can have perfectly logical reasoning applied to false premises. If the premises are false, then the conclusion is worthless. A "fallacy" is usually applying incorrect logic to a valid premise and getting to a wrong or unproven conclusion. Applying correct logic to invalid premises is usually not called a fallacy.

(You could argue the informal fallacy of taking the restaurant owner's word for it when they claim there are no complaints; that would be "appeal to authority" since the restaurant owner should be the authority on that subject).

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What is the fallacy in “If A, then B; not B; therefore not A”?

Looking only at the question, there is no fallacy. The technique is called Denying the Consequent, and this method produces a valid conclusion.

The challenge appears in the specific facts about the restaurant. Here, the reasoning includes questions of causation, which are much more complex.

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Many things can cause A, (e.g., if only single complaint - death of the single complainer, if multiple complainers - no one has listed a complaint, only one type of food being cooked, business only open for short time, etc.)

So if A then B maybe but many things can cause A and B may not be true for everyone.

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Given cause A that leads to B, it does not necessarily follow that without B cause A did not happen. Consider;

If temperatures go up the snow will melt.
No snow melted therefore temperatures did not go up.

This may indeed be true in January, but not true in August. The logic assume the existence of snow to begin with. With a little thought you can come up with other examples of If A then B, but only if other conditions that are not referenced are true as well.

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    I think this could be made much clearer. The point is that A -> B. Not B. Therefore A is formally valid but that the premise A -> B is false because other conditions are necessary. – virmaior Oct 28 '17 at 0:31
  • I agree that your description is more concise. I attempted to answer the question in the vernacular that was used to pose the question. – Patrick O'Hara Nov 6 '17 at 17:11

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