# What is this fallacy? **URL:** \ **Category:** Factual Questions\ **Created:** [July 3, 2009, 12:17am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757 "2009-07-03T00:17:32Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Cagey\_Drifter](https://avatars.discourse-cdn.com/v4/letter/c/b2d939/32.png) [@Cagey\_Drifter](https://boards.straightdope.com/u/Cagey_Drifter)\ **Post date:** [July 3, 2009, 12:17am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/1 "2009-07-03T00:17:32Z")
What is this fallacy? (Or is it a fallacy at all?) > [@](#): > > If you are in an insane asylum, you must be crazy. > You’re in an insane asylum. > Therefore you must be are crazy. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [July 3, 2009, 12:21am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/2 "2009-07-03T00:21:00Z")
Your premise is faulty, but the logic follows. No fallacy. ---
**Author:** ![Randy\_Seltzer](https://avatars.discourse-cdn.com/v4/letter/r/ee7513/32.png) [@Randy\_Seltzer](https://boards.straightdope.com/u/Randy_Seltzer)\ **Post date:** [July 3, 2009, 12:22am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/3 "2009-07-03T00:22:14Z")
Not a fallacy as stated. If A, then B. A. Therefore B. ---
**Author:** ![Indistinguishable](https://avatars.discourse-cdn.com/v4/letter/i/90ced4/32.png) [@Indistinguishable](https://boards.straightdope.com/u/Indistinguishable)\ **Post date:** [July 3, 2009, 12:24am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/4 "2009-07-03T00:24:32Z")
Echoing everyone else: Presumably, the argument is unsound to the extent that its first premise (“if you are in an insane asylum, you must be crazy”) isn’t actually true. But its conclusion does legitimately follow from its premises. ---
**Author:** ![chrisk](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@chrisk](https://boards.straightdope.com/u/chrisk)\ **Post date:** [July 3, 2009, 12:31am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/5 "2009-07-03T00:31:08Z")
I’ll second ‘faulty premise, but that’s not really a fallacy.’ Also, the conclusion is not phrased in correct grammar. You either use ‘must be’ or ‘are’, not both. ---
**Author:** ![Cagey\_Drifter](https://avatars.discourse-cdn.com/v4/letter/c/b2d939/32.png) [@Cagey\_Drifter](https://boards.straightdope.com/u/Cagey_Drifter)\ **Post date:** [July 3, 2009, 1:04am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/6 "2009-07-03T01:04:37Z")
> [@chrisk](#): > > Also, the conclusion is not phrased in correct grammar. You either use ‘must be’ or ‘are’, not both. Uh, yeah, that’s a typo. Thanks, everyone! ---
**Author:** ![Kimmy\_Gibbler](https://avatars.discourse-cdn.com/v4/letter/k/bbe5ce/32.png) [@Kimmy\_Gibbler](https://boards.straightdope.com/u/Kimmy_Gibbler)\ **Post date:** [July 3, 2009, 2:08am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/7 "2009-07-03T02:08:31Z")
> [@Cagey\_Drifter](#): > > Uh, yeah, that’s a typo. > > Thanks, everyone! If you’re looking for a fancy Latin name (one day someone will create a thread on the fallacy that all fallacies and “validities” (as I guess we can call them) have fancy Latin names – as it turns out though, this form, a rather important form, does have such a name), you may call it [_modus ponens_](http://en.wikipedia.org/wiki/Modus_ponens). ---
**Author:** ![Dallas\_Jones](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dallas_jones/32/3277_2.png) [@Dallas\_Jones](https://boards.straightdope.com/u/Dallas_Jones)\ **Post date:** [July 3, 2009, 2:26am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/8 "2009-07-03T02:26:32Z")
This reminds me of one of the best parts of Catch 22 by Joseph Heller. “There was only one catch and that was Catch-22, which specified that a concern for one’s safety in the face of dangers that were real and immediate was the process of a rational mind. Orr was crazy and could be grounded. All he had to do was ask; and as soon as he did, he would no longer be crazy and would have to fly more missions. Orr would be crazy to fly more missions and sane if he didn’t, but if he was sane he had to fly them. If he flew them he was crazy and didn’t have to; but if he didn’t want to he was sane and had to. Yossarian was moved very deeply by the absolute simplicity of this clause of Catch-22 and let out a respectful whistle. “That’s some catch, that Catch-22,” Yossarian observed. “It’s the best there is,” Doc Daneeka agreed.” ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [July 3, 2009, 3:10am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/9 "2009-07-03T03:10:19Z")
The problem with an untrue premise isn’t that the conclusion must therefore be untrue. It’s that any conclusion is possible, true, untrue, ambiguous, or meaningless. ---
**Author:** ![Kimmy\_Gibbler](https://avatars.discourse-cdn.com/v4/letter/k/bbe5ce/32.png) [@Kimmy\_Gibbler](https://boards.straightdope.com/u/Kimmy_Gibbler)\ **Post date:** [July 3, 2009, 7:14pm UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/10 "2009-07-03T19:14:27Z")
> [@Exapno\_Mapcase](#): > > The problem with an untrue premise isn’t that the conclusion must therefore be untrue. It’s that any conclusion is possible, true, untrue, ambiguous, or meaningless. Or in fancy Latin, [_ex falso quodlibet_](http://en.wikipedia.org/wiki/Ex_falso_quodlibet). ---
**Author:** ![AskNott](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/asknott/32/5790_2.png) [@AskNott](https://boards.straightdope.com/u/AskNott)\ **Post date:** [July 3, 2009, 8:22pm UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/11 "2009-07-03T20:22:57Z")
Maybe I’m wrong, but I think it might be (what was originally called) _begging the question_. That is, the starting premise includes what you intend to prove. These days, the phrase “begging the question” is widely given a different meaning. It causes screaming and gnashing of teeth among word carvers. The new meaning is so widespread that some of us have surrendered to the change. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [July 4, 2009, 4:16am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/12 "2009-07-04T04:16:32Z")
> [@AskNott](#): > > Maybe I’m wrong, but I think it might be (what was originally called) _begging the question_. That is, the starting premise includes what you intend to prove. It isn’t, though: The premise is a conditional, the next statement is saying the first half of the conditional is true, so the third statement says the second half of the conditional is true. That’s a valid syllogism. ---
**Author:** ![Indistinguishable](https://avatars.discourse-cdn.com/v4/letter/i/90ced4/32.png) [@Indistinguishable](https://boards.straightdope.com/u/Indistinguishable)\ **Post date:** [July 4, 2009, 4:17am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/13 "2009-07-04T04:17:25Z")
Well, even any unmistakable instance of begging the question produces a valid inference, at least as long as one is explicit about the premises being begged. The accusation is then just about the usefulness of such an argument (in convincing anyone of anything they didn’t already believe), and this one is certainly pretty useless. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [July 4, 2009, 4:27am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/14 "2009-07-04T04:27:07Z")
> [@Indistinguishable](#): > > Well, even any unmistakable instance of begging the question produces a valid inference. This still isn’t _petitio principii_, though, it’s a valid argument from a flawed premise. For everyone else following along at home: _Petitio principii_ is the Latin phrase for ‘begging the question’, which is only used in the technical (logical) sense in this language. A better name for it is a circular argument, because it does go around in a neat little circle, moving a bit but ending up right where it began. [Here’s a good page on the topic with plenty of examples.](http://philosophy.lander.edu/logic/circular.html) This is an interesting one: > [@](#): > > “A law has been named after Engel in light of this work. Engel’s law states that ‘the poorer the individual, the family or a people, the greater must be the percentage of the income needed for the maintenance of physical sustenance, and of this a greater proportion must be allowed for food.’ It is odd to find this as a law, since **Engel had used the proportion of outgoings on food as the measure of material standard of living**.” Ian Hacking, _The Taming of Chance_, (Cambridge Univ. Press, 1990), 140. In case you missed it: Engel came to the conclusion that the poor spend more of their money on food, because previously he had defined ‘the poor’ as those who spend more of their money on food. ---
**Author:** ![Indistinguishable](https://avatars.discourse-cdn.com/v4/letter/i/90ced4/32.png) [@Indistinguishable](https://boards.straightdope.com/u/Indistinguishable)\ **Post date:** [July 4, 2009, 4:33am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/15 "2009-07-04T04:33:36Z")
> [@Derleth](#): > > This still isn’t _petitio principii_, though, it’s a valid argument from a flawed premise. But so is petitio principii, if one acknowledges as a premise the one being “begged”. I am perfectly willing to call the OP’s flaw an implicit “begging of the question”; it’s not like the term is very formally defined, and certainly the problem with this argument is of the right flavor. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [July 4, 2009, 4:46am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/16 "2009-07-04T04:46:06Z")
> [@Indistinguishable](#): > > But so is petitio principii, if one acknowledges as a premise the one being “begged”. I am perfectly willing to call the OP’s flaw an implicit “begging of the question”; it’s not like the term is very formally defined, and certainly the problem with this argument is of the right flavor. This is true, but it misses the mark because the argument in question isn’t _vacuous_. It’s just as meaningful as the syllogism “Everything in my website will be indexed by Google. That shot of me doing body shoots off my boss’s wife is in my website. Therefore, it will be indexed by Google. Corollary: I’m going to lose my job and I might get my ass kicked.” A circular argument is formally valid but meaningless. The OP’s argument is formally valid and meaningful. Therefore, it cannot be circular. ---
**Author:** ![Indistinguishable](https://avatars.discourse-cdn.com/v4/letter/i/90ced4/32.png) [@Indistinguishable](https://boards.straightdope.com/u/Indistinguishable)\ **Post date:** [July 4, 2009, 5:01am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/17 "2009-07-04T05:01:39Z")
Which of the following arguments are meaningful and which are meaningless? Argument #1: Premise 1: I like strawberries Premise 2: I like bananas Cocnlusion: I like strawberries and I like bananas Argument #2: Premise 1: I like strawberries and I like bananas Conclusion: I like strawberries Argument #3: Premise 1: I like strawberries Conclusion: I like strawberries or I like bananas (perhaps both) Argument #4 Premise 1: In my left hand, I have 5 strawberries Premise 2: In my right hand, I have 2 strawberries Conclusion: In my hands, I have 7 strawberries Argument #5 Premise 1: I have 4 bananas Conclusion: I have an even number of bananas I could well imagine any of these arguments being labelled with the accusation of “begging the question” or “valid but vacuously circular”, particularly if one were to present them less formally so that some of the premises become enthymematic, and yet I could also just as well imagine construing each of these as quite “meaningful”. For that matter, I can also imagine construing them as “meaningless”, and also construing the OP as “meaningless”. It all depends on the context. I don’t think there are grounds for some principledly sharp distinction between “meaningful” and “meaningless” in the way you apparently mean, nor any corresponding distinction between the kind of “The conclusion is implicitly there in the premises” which is requisite for any argument to be valid and the kind which we would label question-begging. It’s in the eye of the beholder, the use to which the argument is being put, the extent to which it could possibly be persuasive or a novel discovery, and so on. ---
**Author:** ![Indistinguishable](https://avatars.discourse-cdn.com/v4/letter/i/90ced4/32.png) [@Indistinguishable](https://boards.straightdope.com/u/Indistinguishable)\ **Post date:** [July 4, 2009, 5:12am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/18 "2009-07-04T05:12:45Z")
(A minor thing, but I suppose I meant “circularly vacuous” rather than “vacuously circular”…) ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [July 4, 2009, 5:35am UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/19 "2009-07-04T05:35:16Z")
On further thought, I suppose I agree with you. ---
**Author:** ![Bisected8](https://avatars.discourse-cdn.com/v4/letter/b/a4c791/32.png) [@Bisected8](https://boards.straightdope.com/u/Bisected8)\ **Post date:** [July 4, 2009, 1:00pm UTC](https://boards.straightdope.com/t/what-is-this-fallacy/501757/20 "2009-07-04T13:00:26Z")
> [@Indistinguishable](#): > > Which of the following arguments are meaningful and which are meaningless? > > Argument #1: > Premise 1: I like strawberries > Premise 2: I like bananas > Cocnlusion: I like strawberries and I like bananas > > Argument #2: > Premise 1: I like strawberries and I like bananas > Conclusion: I like strawberries > > Argument #3: > Premise 1: I like strawberries > Conclusion: I like strawberries or I like bananas (perhaps both) > > Argument #4 > Premise 1: In my left hand, I have 5 strawberries > Premise 2: In my right hand, I have 2 strawberries > Conclusion: In my hands, I have 7 strawberries > > Argument #5 > Premise 1: I have 4 bananas > Conclusion: I have an even number of bananas > > I could well imagine any of these arguments being labelled with the accusation of “begging the question” or “valid but vacuously circular”, particularly if one were to present them less formally so that some of the premises become enthymematic, and yet I could also just as well imagine construing each of these as quite “meaningful”. For that matter, I can also imagine construing them as “meaningless”, and also construing the OP as “meaningless”. It all depends on the context. I don’t think there are grounds for some principledly sharp distinction between “meaningful” and “meaningless” in the way you apparently mean, nor any corresponding distinction between the kind of “The conclusion is implicitly there in the premises” which is requisite for any argument to be valid and the kind which we would label question-begging. It’s in the eye of the beholder, the use to which the argument is being put, the extent to which it could possibly be persuasive or a novel discovery, and so on. Nope, there are formal definitions for an accurate (“Sound”) argument. A sound argument has to be both valid and true. Which for the purpose of logic are defined as; Valid: To be valid the chain of reasoning must be sound. The logic used must be effective and…well…logical. An argument with invalid logic is a fallocy. Truth: For an argument to be “true”, the premises must be true, note that a faulty premise can still result in a true conclusion. The later case does not make an argument true. Sound: If the argument is both valid and true then it can be considered a sound argument. If it has just one or the other or neither, it isn’t sound. [Next page](https://boards.straightdope.com/t/what-is-this-fallacy/501757.md?page=2)