## Is the argument that a claim is "too strange to be made up" an appeal to logos or pathos?

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When someone tries to persuade you of the truth of something they said and they use the argument that it is too strange to be made up (or any variations of this, such as "too complicated to be fiction"), is that person making an appeal to your logical reasoning (logos) or to your emotions (pathos)?

– David Cary – 2013-05-16T13:02:26.403

4I think I asked a professor this question once, and he thought it was funny too. I like this question and its humor. – davidlowryduda – 2011-07-31T18:03:53.193

Related: Too Good to Be True

– Steve Moser – 2016-01-24T15:37:24.097

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This is an appeal to Bayesian statistics. The speaker cannot possibly mean that it is logically impossible for someone to make up whatever-it-is, so they must be meaning that it's extremely improbable. Thus, what they are saying is, effectively, when you are computing the chance of various models given the data, make sure you weight your prior for the "made it up" case appropriately (i.e. very low). Given that, a priori, it's very unlikely that anyone made that thing up, other explanations (even very improbable ones) begin to look correspondingly more favorable.

So it's entirely valid logically (albeit indirect via statistics).

However, although it's potentially valid when doing statistical reasoning, it's not necessarily the case that people intend for you (or themselves) to do it that way. People could be hoping that you will have the same emotional reaction they did: "OMG! No way!!" and then set the a priori probability to zero and thus promote some other perhaps-even-more-wildly-unlikely scenario to be the "best explanation". The correct thing to do may be to recognize that although it's unlikely that someone could come up with such things, everything else is even more unlikely, and thus it-was-made-up is the best explanation (given available evidence).

I'm not sure that a scenario this complicated is well captured by the terms logos, pathos, or ethos. It is like ethos in that arguments from ethos are also arguments about weighting a priori probabilities in a Bayesian framework, but there is no trustworthiness involved here. (Trust is one reason you might adjust your priors.) Although there is logically sound information contained in such an argument, it is usually presented in a very different form than typical appeals to the intellect. Almost no-one is consciously aware of their distribution of prior probabilities, so a more intuitive presentation tends to be more effective (though this says nothing about the validity...).

I see the point you're making. But to play devil's advocate, consider a situation in which someone tells the truth 10% of the time, and the other 90% of the time tells a random lie from among ten million. For any given lie, it's highly unlikely that that the person will tell that particular lie. But it's also more likely that the person is lying than telling the truth. So the relevant question is not whether the speaker could have made up a particular lie, but is rather how often the speaker lies -- a matter of simple trustworthiness. – senderle – 2014-04-25T17:00:29.990

@senderle - I'm not sure that this devil is arguing against anything I said...? – Rex Kerr – 2014-04-25T21:17:32.220

I just meant that if this argument does work, it works in the same way an appeal to ethos works -- i.e. as an appeal to trustworthiness. – senderle – 2014-04-26T00:03:45.927

@senderle - No, the question is postulating a lack of trustworthiness and rejecting it as a poor model. The claim "this is too weird to be made up" is not a statement about someone lying 100% of the time that fails if they lie only 10% of the time. It's a statement that nobody could make that up even if they tried, whether this is the first lie they've ever told or whether they lie about everything all the time. My answer assumes this setup. So I'm not sure you actually do see the point I'm making. – Rex Kerr – 2014-04-26T03:02:21.113

Well maybe not. Perhaps I would understand it more clearly if you showed the exact mathematical form you're thinking of. – senderle – 2014-04-26T15:19:44.150

@senderle - Let S be a statement. Let u(.) measure how unexpected (strange, complicated, etc.) the statement is. Let {T} be the set of statements you expect to encounter that are generated by people. Then the statement is that p(u(S) < min[t in T]{u(t)}) is small. That is, out of all the stuff people might make up and say to you (expecting you to believe it), this one is too unexpected. (The probability is computed over all possible sets T in this formulation.) – Rex Kerr – 2014-04-26T20:01:56.303

Oh. When you said "Baysian statistics" I was thinking something more like P(person is lying|claim=X) = P(claim=X|person is lying)P(person is lying) / P(claim=X). So the statement would be that P(claim=X|person is lying) is very low -- that is, that if the person is lying, then the probability of the person making claim X is very low. – senderle – 2014-04-26T21:30:15.690

@senderle - On rereading, I realize I got one sign (actually min/bax) backwards. If u is unexpectedness (rather than expectedness), then I should have said p(u(S) < max[t in T]{u(t)}). That is, it's unlikely that S is less weird than the weirdest made-up thing people would actually say (and try to get you to believe). – Rex Kerr – 2016-01-24T20:54:58.590

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I don't think it's either an appeal to logos or pathos, but rather an appeal to ethos.

Here's a quick overview of the three classic types of argumentative appeals:

Logos: an appeal to the facts and logic used to support a claim (both inductive and deductive)
Ethos: an appeal to the credibility of the source, including the speaker or author
Pathos: an appeal to the emotions and/or individual motivations of the listener, particularly characterized by the use of vivid language with lots of sensory details

The justification that an argument is true because it is "too strange to be made up" definitely sounds like an appeal to the credibility of the speaker. It sounds to me like you're saying "regardless of whether or not you think I'm a liar, I couldn't  have possibly  made this  one up!"

It's not a particularly strong or convincing argument, mind you, but I think it is clearly an appeal to the ethos of the speaker rather than an appeal to the inherent logic of the argument or an attempt to invoke strong emotions on the part of the listener.

where are these 'appeals' laid out (do you have a reference?) – Mitch – 2011-07-29T14:05:19.920

I believe Aristotle is the original source for these; a quick summary can be found relatively easily e.g. here http://courses.durhamtech.edu/perkins/aris.html

– Joseph Weissman – 2011-07-29T19:20:45.957

1@Mitch: Yes, Joseph is right: the three argumentative appeals were elucidated by Aristotle in On Rhetoric. He calls them the three modes of persuasion, and says that strong arguments have a balance of all three, although insists that logos is essential for a strong and balanced argument. He also observes that these appeals can all be misused, creating arguments that are not credible. So the mere presence of these appeals is not sufficient to create a logical argument. (And my answer was not intended to validate the original argument in the question.) – Cody Gray – 2011-07-29T21:38:52.473

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The original text of Aristotle's On Rhetoric is available here online. Pay special attention to the end of Book 1.

– Cody Gray – 2011-07-29T21:39:52.020

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I think this would be an example of a fallacy known as a Red Herring.

A Red Herring is a fallacy in which an irrelevant topic is presented in order to divert attention from the original issue. The basic idea is to "win" an argument by leading attention away from the argument and to another topic.

That the argument is complicated is irrelevant to the truth of the argument.