Is it a logical fallacy to discredit a conclusion because proponents of the said conclusion disagree with one another as to what are valid arguments for that conclusion?

If so, what is the name for this fallacy?


Person A: The sky is blue because the atmosphere refracts blue light waves differently than other colors.

Person B: No, the sky is blue because the atmosphere is made of smurf-ghosts.

Person C: Since there is disagreement between Person A and B, the argument that the sky is blue is weak.

  • 1
    "If they disagree, neither of them has a good argument" is such a specific false conditional I'm tempted to just call it an informal fallacy (i.e. a false premise rather than a logically invalid premises-to-conclusion path); but if this example has a name, fair enough.
    – J.G.
    Apr 16, 2022 at 16:31
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    Generally the person who rejects a conclusion or arrives at a bad conclusion with no justification has made an error in reasoning. In this case the two people in your example are not committing the fallacy. People jumping to the conclusion the argument is weak or perhaps there is no answer to the topic is common. People do exactly that with Philosophy. Philosophers disagree about everything thing so Philiosophy has no answers & useless. One fallacy is non sequitur. There could be others as well.
    – Logikal
    Apr 16, 2022 at 20:55

1 Answer 1



I would say no based on the exact wording. If two expert witness have different arguments to get to a conclusion, then it may very well be that the argument to get the conclusion is weak. It would absolutely be a fallacy if instead of...

the argument that the sky is blue is weak.

you were to have written

the sky is not blue.

And this is because the nature of a fallacy. A fallacy is an argument, at least one explicit premise leads to a faulty conclusion. Obviously if two experts have differing claims as to why the sky is blue, then to conclude the sky isn't blue would be specious. But, if one defines a "weak argument" as argument that fails to persuade, then to have two experts who cannot persuade each other seems to confirm that both arguments are somehow weak. In fact, the less agreement there is among experts about the why, the more evidence accumulates that no argument is strong.

Remember, as written, the claim of person C has nothing to do with the color of the sky, but rather the strength of the arguments. If we were to reformulate from C's perspective, to get to C's conclusion, it would be more along the lines of:

P1. Expert A's argument does not convince expert B.
P2. Expert B's argument does not convince expert A.
C. The argument to get to the conclusion shared by A and B is weak.

In fact, I would say not only is C not engaging in fallacy, but that C is making the start of a compelling argument.

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