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Evidence of things not seen.
February 24, 2010 2:29 PM   Subscribe

Is there a specific name for a logical fallacy where the lack of evidence for something (or the abundance of evidence its opposite) is claimed to actually support the assertion? An example might be claiming that the lack of evidence of a conspiracy is actually evidence of the conspiracy and/or its size and strength.

Here's a real life example I stumbled upon recently: I actually find the near-universal agreement in the "credible" scientific community to be the best case against believing in global warming. How many correct scientific revelations have been accepted so quickly and so completely by science?
posted by spaltavian to Writing & Language (19 answers total) 10 users marked this as a favorite
 
A reverse of an appeal to popularity.
posted by GuyZero at 2:35 PM on February 24, 2010


The magic rock fallacy.
posted by odinsdream at 2:35 PM on February 24, 2010


Sounds less like a logical fallacy than a straight up conspiracy theory.
posted by ook at 2:42 PM on February 24, 2010


I can see this as a larger set of "too much evidence" fallacies, such as:

"Luann's fingerprints were found on the knife, and the bloody footprints match hers? Well, that proves she didn't do it, she'd never be that sloppy."

"His tax returns don't exaggerate or have any irregularities whatsoever. He must be hiding something!"

"His house is a total dump and his car is twenty years old. That proves he must be hiding a ton of money somewhere!"

Unfortunately, the closest I can find to a name for it is a very contrary version of Missing the Point.
posted by lore at 2:56 PM on February 24, 2010


I would think of it as, "the exception proves the rule," but people are usually serious when they say that.

But that's what it comes down to: "Because of this evidence against my view, my view must be correct."
posted by drjimmy11 at 3:15 PM on February 24, 2010


It's an Affirming the consequent.

1) For this conspiracy to work you need to get all the public faces to agree.
2) All the public faces agree.

Therefore, it's a conspiracy.
posted by Tell Me No Lies at 3:17 PM on February 24, 2010 [2 favorites]


I see this as different than affirming the consequent, which is:
1. If P, then Q.
2. Q.
3. Therefore, P.

The way I see it, what we have here is
1. If P, then Q
2. P. Lots of P. Overwhelming P.
3. Therefore, not Q.

To turn that into an example:
1. If all the evidence points to global warming being true, then global warming is true
2. There is lots of evidence that global warming is true
3. Therefore, global warming is false because CONSPIRACY!

I'm not sure what to call this. I think it might be Bulverism, but I'm more inclined to call it "grasping at straws."
posted by adamrice at 3:36 PM on February 24, 2010


adamrice, I see where you are coming from, but I think maybe I used a poor example. From the original question:

An example might be claiming that the lack of evidence of a conspiracy is actually evidence of the conspiracy

1) If there was a conspiracy(p), there would be no evidence of a conspiracy(q).
2) There is no evidence of a conspiracy(q).
3) Therefore there is a conspiracy(p)
posted by Tell Me No Lies at 3:44 PM on February 24, 2010 [1 favorite]


Is there a specific name for a logical fallacy where the lack of evidence for something (or the abundance of evidence its opposite) is claimed to actually support the assertion?

That part in the parenthetical seems to be what you're really asking about (based on your global warming example), and it's very different from "lack of evidence for something." If I understand you correctly, you're not talking about someone arguing: "There isn't any evidence for global warming; therefore, there is no global warming." You're talking about someone arguing: "We've been presented with so much seemingly consistent evidence for global warming that it looks like a conspiracy theory."

I agree with ook: this isn't strictly a logical fallacy -- it's a conspiracy theory. Whether you're convinced by the conspiracy theory depends on your perception of the facts, but "logic" isn't going to be determinative. It's not illogical to conclude that an abundance of supposed evidence that seems too perfect to be legitimate, plus a lack of skepticism among the experts, is a sign that the experts are conspiring to affirm a false thesis. It could be a false view of global warming without being the result of a logical fallacy. Not all misreadings of the facts are logical fallacies. This isn't to deny that global warming deniers are making any logical fallacies (I'd imagine they are), but I'm not convinced that you've identified one.
posted by Jaltcoh at 3:47 PM on February 24, 2010


It sounds like an appeal to ignorance.
posted by lhude sing cuccu at 3:49 PM on February 24, 2010


It's a type of reasoning that's characteristic of paranoia. (I have been sort of writing a paper on this for a few years now, haven't found anything very useful on it beyond what I've generated myself, so I'll be pleased if you get good answers here.)

Similar to but *not* the same as Argument from ignorance - evidence does not show x is false, therefore x must be true. Example, we searched the house and didn't find anything that cleared him of being a terrorist, therefore he must be a terrorist.
posted by LobsterMitten at 3:53 PM on February 24, 2010


Jaltcoh: That part in the parenthetical seems to be what you're really asking about (based on your global warming example), and it's very different from "lack of evidence for something." If I understand you correctly, you're not talking about someone arguing: "There isn't any evidence for global warming; therefore, there is no global warming."

They aren't very different. The example you just gave there is not what my question without the parenthetical would mean.

If you read my question without the parenthetical, it reads "Is there a specific name for a logical fallacy where the lack of evidence for something is claimed to actually support the assertion?" Which would translate to: "There's no evidence that x exists, therefore x exists". The situation in the parenthetical would translate to "There's a lot of widely accepted evidence for y, the opposite of x. Therefore, y exists."

The conspiracy example would fit into the non-parenthetical model, whereas the global warming example would fit into the parenthetical model.
posted by spaltavian at 4:03 PM on February 24, 2010


I stand by appeal to popularity as the argument is essentially that the validity of the assertion is based on how popular or unpopular it is.
posted by GuyZero at 4:13 PM on February 24, 2010


Signs of Contradiction?
posted by Stylus Happenstance at 4:18 PM on February 24, 2010


If you're interested in just a general "lack of evidence for x shows that x is false" or equivalently "lack of evidence against y shows that y is true", that's argument from ignorance.

If you're interested specifically in the reasoning involved in claims of conspiracy, it's a different thing. A conspiracy theory takes evidence that seems like it should contradict x, and turns it into evidence for x. I do not know of a fallacy "name" for this.
posted by LobsterMitten at 4:31 PM on February 24, 2010


And as to your example below the fold, maybe the person who said that is really using a principle like this:

- Good science does not have "too much" agreement - Science does not move in lockstep, so if science seems to move in lockstep that should raise suspicions that there's something improper or unscientific going on.

What should we make of this principle?
Sometimes this principle is right - sometimes evidence can be "too good", for example if data line up too perfectly, that can tip reviewers off that there is fraud happening. And, sometimes widespread agreement is indeed due to epistemic blinders that may have to do with incorrect old theories, or may have to do with matters separate from science altogether (eg racial and social prejudice shaped early quantitative psychology in a way that led to incorrect results being widely accepted).

But -- sometimes widespread agreement is due to very very strong evidence that has convinced people. The theory of plate tectonics was accepted within a relatively short time period in the 1960s-70s, for example.
posted by LobsterMitten at 4:40 PM on February 24, 2010


I believe it is shifting the burden of proof:

The burden of proof is always on the person making an assertion or proposition. Shifting the burden of proof, a special case of Argumentum ad Ignorantiam, is the fallacy of putting the burden of proof on the person who denies or questions the assertion being made. The source of the fallacy is the assumption that something is true unless proven otherwise.
posted by torquemaniac at 5:08 PM on February 24, 2010 [1 favorite]


Jaltcoh: ... They aren't very different. The example you just gave there is not what my question without the parenthetical would mean.

OK, sorry, you're right that I misinterpreted you. I still say the global warming example isn't a fallacy. Also, does anyone actually argue, "There is no evidence for X; therefore, X exists?" That seems quite different from saying, "There's so much evidence for X that the evidence is probably bogus." The latter statement at least could be logical, depending on the circumstances. (For instance, if someone shows me more and more "evidence" that ancient Greek polytheism is true, I won't believe them -- I'll just think it proves they like to make stuff up, and I don't think this is a fallacy. I would apply this to many religious, mystical, and pseudo-scientific views.) But the former statement ("This is true because there's no evidence for it") is so illogical that I question whether anyone ever uses it as an argument.
posted by Jaltcoh at 5:35 PM on February 24, 2010


This doesn't cleanly fit into any of the stereotypical fallacies. No point in trying to cram it into one of them. Not all instances of poor reasoning are instances of named fallacies.

A free diatribe on the side: I kind of hate lists of fallacies. The lists never agree. And the fallacies in any one list tend to overlap; they conflate various sorts of norms of rationality; they assume outmoded models of rationality; they assume and conflate various theories of justification; they purport to be universal but not all instances of the fallacy schemas should be considered fallacies; they're not motivated by current psychological models of reasoning, etc. Lists of fallacies are helpful for bootstrapping someone into a position in which they can start identifying good reasoning from bad reasoning---they're useful in getting someone to start thinking critically. But they are very bad at carving the space of arguments at the joints and categorically distinguishing good arguments from bad arguments. And I do not think they are that rhetorically useful in getting others to change their minds. If you can explain why an argument is bad, there's little point in trying to attach the name of a fallacy to it.

Anyway, there definitely won't be a general fallacy with a tidy name that covers the reasoning behind your conspiracy theorist. I think your case would be considered a little misdescribed by a contemporary epistemologist, because they tend to use the word 'evidence' a little differently than you do. Facts such as "no conspiracy group has appeared on TV claiming that they control the stock market" do count as evidence that there is a conspiracy that perfectly covers its tracks. The reason that the conclusion is unwarranted, however, is because the prior probability of there being a conspiracy that perfectly covers its tracks is much lower than the prior probability that there isn't a conspiracy. So your example could be seen as a confusion about the likelihood of states of affairs rather than a fallacy of reasoning.

It's also not obvious to me that the reasoning in your argument below the fold is necessarily bad. I think it's unsound (the correct response to the rhetorical question at the end is "often"), but the reasoning isn't obviously terrible.

I think LobsterMitten's mention of paranoid reasoning is interesting. (That paper sounds cool, LM.) Some cases of paranoid reasoning are described as instances of twisted self-deception, so there's a term that might be worth looking up....
posted by painquale at 11:52 AM on February 25, 2010


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