I'm wondering if there is a terminology for the following logical fallacy:

Joe: Statement "X" must be true because it is clearly laid out as such in mutually reliable source "Y".

Sam: Joe, the statement "X" seems outlandish and therefore it ought to be rejected in its own right.

Joe: It is not me postulating or forcing statement "X", rather it is mutually reliable source "Y" that indicates it is true. Therefore in as much as you respect source "Y", you shouldn't question me. Rather, you should reconsider if you're own presupposition about statement "X" is compatible with mutually agreed source "Y".

I know it's a little bit abstract... if there's any way I can modify it please help...

  • 1
    Wait...which one is committing the fallacy?
    – Mitch
    Jan 8, 2020 at 2:30
  • 1
    Which fallacy this is, and who committs it, depends on what "mutually agreeable" means. If Sam and Joe agreed to take Y's claims as premises, and Sam is reneging on it on the basis of "seemings" he is committing special pleading, calling an exception when it suits him. If, on the other hand, Y is merely a typically reliable but fallible joint reference then Joe is committing genetic fallacy, prejudging a claim by its source.
    – Conifold
    Jan 8, 2020 at 3:06
  • 1
    I have the same question as Mitch. Jan 8, 2020 at 5:47
  • Mutually reliable means that Both Sam and Joe agree that source Y is authoritative.
    – Big Mouth
    Jan 8, 2020 at 18:14

4 Answers 4


Sam's statement:

Joe, the statement "X" seems outlandish and therefore it ought to be rejected in its own right.

is an example of the Appeal to Incredulity.

This fallacy is attributed to those who reject a proposition because they can't comprehend it being true, or who accept a proposition because they can't comprehend it being false.

Joe's statement is an Appeal to/Argument from Authority.

Statement "X" must be true because it is clearly laid out as such in mutually reliable source "Y".

Depending upon your source, an appeal to authority is either always fallacious or sometimes fallacious. Some deem the ATA fallacious only when the authority is not widely acknowledged or irrelevant to the claim in question. Others believe the ATA is fallacious all the time, because any authority can misrepresent and/or misinterpret the data they are charged with assessing. Prior performance is no guarantee of continued performance. In short, the reputational status of an organisation is no guarantee against error or deception.


Let's see. You say the exchange is logical, and that there lies substantive evidence of why Joe is right—which essentially is the conclusion.

The term I can think of is Syllogism. According to MW, the term is defined as:

1 : a deductive scheme of a formal argument consisting of a major and a minor premise and a conclusion (as in "every virtue is laudable; kindness is a virtue; therefore kindness is laudable")

2 : a subtle, specious, or crafty argument

3 : deductive reasoning

I think both (1) and (3) are describe the situation aptly.


As people have hinted in the comments. It kinda depends on what they are arguing about.

Joe could commit a fallacy of "appeal to authority" or apparently a "genetic fallacy" or whatever you want to call it. The point being he bases his argument not on premises and conclusions but upon the authority and reputation of a source. And no expert is beyond doubt.

Though if he's not actually just using that as an authority, but as a reference to something that is mutually agreed upon or even an premise, then this might not be a fallacy at all but rather a good argument, showing a contradiction indicating that something in your argument doesn't work as expected. So in that case Sam would be the person committing a fallacy by rejecting an option just because it doesn't fit his assumptions.

Or he might be right to do so because it is actually impossible due to other reasons and Joe is committing a non sequitur along the way either with the "mutually accepted source" or elsewhere.


My two sikkas

When we rely on an authority, it usually isn't an argument that's the issue, it's more often a statement. So if an expert/authority claims (say) selenium cures dandruff, we're usually not told why; instead the claim appears alone, by itself, sans evidence.

If an authority/expert offers evidence/an argument, we should immediately shift our attention from the credentials the expert/authority has (making him an authority/expert) to the argument/evidence itself.

@Futilitarian mentions The Fallacy of Appeal to Authority (argumentum ad verecundiam). He's on target. The other guy commits The Divine Fallacy* ("outlandish", he says). However, it isn't clear whether he found an inconsistency in the argument (an inconsistency is, at some level, outlandish.

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