I've seen philosophical arguments descriped as 'argumentum ad lapidem', but never quite understood what the criticism is trying to indicate. As best I can tell, it's a dismissal of an argument with no good justification. Could anybody expand a little on the precise nature of this logical fallacy?

1 Answer 1


According to the Wikipedia definition:

Ad lapidem (Latin: "to the stone") is a logical fallacy that consists in dismissing a statement as absurd without giving proof of its absurdity.

The Latin name is doubly confusing in that it has a fairly modern origin and in that it relates to a specific example:

The name of this fallacy is attributed to Dr. Samuel Johnson, who refuted Bishop Berkeley's immaterialist philosophy (that there are no material objects, only minds and ideas in those minds), by kicking a large stone and asserting, "I refute it thus."

Now as an effective and memorable rhetorical tactic, Dr. Johnson found an excellent way to make his point. The problem comes when examining the content of his logical argument. What he suggests by his demonstration is that of course there are material objects: we can feel them and see them and interact with them. But if Bishop Berkeley objected that the sensation of feeling, seeing and interacting with objects could simply be the result of, for instance, imagination, Dr. Johnson would need to deal directly with that objection. (I don't know either if Bishop Berkeley made such an objection or if Dr. Johnson offered a response, but for the sake of the illustration, let's assume the first did and the later didn't.)

It's not always incorrect to use arguments that are in the form of logical fallacies, as the example of kicking a stone illustrates. For most of us, the simple demonstration is effective at getting the point across. But when you consider the opposite viewpoint, ad lapidem does not satisfy an objection or compel agreement. It may be useful for scoring points in a debate, but not useful in either finding common ground or discovering the truth. Pointing out a fallacious argument should redirect the proponent of the position to try another method of arguing that does not entail a logical fallacy.

Dr. Johnson could have corrected his argumentum ad lapidem (and perhaps he did) by suggesting some other reason not to accept immaterialism.

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    @Jon, I've transformed the monospace-block (a habit gained from SO, I presume?) in your question to an inline block quote (just use a single > to offset a block, but note this also has the advantage of letting you embed quotes within one another.) Great answer, by the way!
    – Joseph Weissman
    Jun 13, 2011 at 23:52
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    @Joe: Very perceptive and a good use of the edit power. I'm not 100% pleased with the result as it appears the two paragraphs are connected on Wikipedia. I'd love to use a bit of LaTeX and make it look just so. Jun 13, 2011 at 23:55
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    You could add your ellipsis back, or interpose a connecting phrase like, "Wikipedia also relates a old story traditionally used to introduce this fallacy" or something. (Regarding Tex, keep in mind it's an extremely heavy module...)
    – Joseph Weissman
    Jun 14, 2011 at 0:03
  • @Joe: Good suggestion. (And my idle desires are in no way a feature request. ;-) Jun 14, 2011 at 0:08
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    You give Johnson a lot of undue credit here. His argument entirely fails to respond to Berkeley, who easily addressed this supposed criticism in his Principles of Human Knowledge One could compare it to criticizing special relativity by dropping an apple - it proves nothing, and would only demonstrates your complete lack of understanding of the subject. Berkeley is easy to object to, and you can ultimately disregard him like Johnson if you wish, but he is far harder to prove wrong than one might initially think. This isn't to say it's impossible, but Johnson certainly didn't come close.
    – dimo414
    Jun 16, 2011 at 3:00

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