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Because there is no observable certainty other than the existence of thought

Someone who is teaching a college philosophy class writes:

We discussed Descartes’ Meditations on First Philosophy last week — specifically, concerning the existence of God — and I had students write down their best proof for God’s existence in one minute, independent of their beliefs. Attached is a particularly funny response:

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Another good one was the blank sheet of paper that a student handed in…


  1. seldomawake says:

    Good attempt! The ol’ supersensible as incomprehensible fallacy has tripped so many.

    There is a Real Possibility that a sharp dose of early Wittgenstein will find fertile ground here.

  2. Keith O'Rourke says:

    Here’s CS Peirce’s attempt.

    (Actually a very good discussion of the logic of science as a prelude.)

  3. vonjd says:

    I think both are exceptionally clever answers :-)

  4. You said, dear Descartes, that “je pense, donc je suis,”
    Deriving existence from uncertainty.
    Now, you are gone, and we say, “au revoir,”
    Doubtless we think, René, therefore we R.

    From Chapter 3, about the programming language R, of DBDA2E.

  5. Xi'an says:

    Great ones. Except we cannot even prove the existence of thought…

    • Martha says:

      “Except we cannot even prove the existence of thought…”

      Still, we may have a subjective prior on the existence of thought, so possibly we can do a Bayesian analysis …

      • Andrew says:


        Data-based prior, please! Or, if you must refer to “subjective prior,” please also talk about “subjective likelihood function,” “subjective logistic regression,” “subjective additive linear model,” etc.

        • JD says:


          I can’t tell: Is your response here an objection to the use of personal probability for this problem, or just with the terminology “subjective”?


          • Andrew says:


            I have two objections. First, I think our models should be data-based as much as possible so I don’t like the attitude that the prior is something that people just pull out of their heads. Second, to the extent that specifying a Bayesian prior distribution is subjective, so are the other choices in a model: the subjective logistic regression, subjective additive model, etc.

            To say it again: From a normative perspective, I want Bayesian priors to be data-based, and I worry that the “subjectivist” terminology is used by people to get themselves off the hook and think that any prior they choose is ok. From a descriptive perspective, I think it’s inaccurate and misleading to single out the prior distribution as having some subjective status that is not present in other aspects of a statistical model or statistical procedure.

  6. Davester says:

    As a believer I agree with what the student wrote. Proving the existence of God is a non-empirical, personal matter involving faith. I believe in God because of experiential events involving the Spirit. My faith is not based on external events.

  7. Chris G says:

    No! No, you didn’t! You published a page from David Brooks’ secret diary! He’s gonna be really angry.

  8. Ehler says:

    …yeah, straying into philosophy/metaphysics is risky for statisticians because objective probability is impossible to prove. Philosophic issues mesh poorly with worldly science practitioners.

    Quantifying limited subjective “data” does not make it objective.
    That Quantum Bayesianism/QBism stuff really muddies the waters pretty well.

    The kid’s assertion in the Philosophy class has a lot of formal philosophical support — one’s perceived existence confirms only that the subjective probability of such a perception is non-zero.
    All else is non-verifiable, objectively. Bummer

    (“Reality is an illusion” — Albert Einstein)

  9. D.O. says:

    I am glad my professors never asked me to write my best one minute proof of the Fermat theorem. If I think about it, not even the most trivial theorem. Why is holding the concept of god in such low regard?

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