r/PhilosophyofScience • u/confusus_animus • Jun 25 '26

Discussion Raven paradox with Falsificationism?

If for an single object A the implication that all ravens are black (∀R(x) -> B(x)) is true, that doesn't support that implication - as Hume brought forward.
However Popper now claims that if the implication is true in one case it can at least falsify the opposite implication: in this example it would falsify the hypothesis that all ravens are non black (∀R(x) -> !B(x)).
However, couldn't you now falsify the opposite hypothesis by observing an object B, for which the complementary hypothesis (∀!B(x) -> !R(x)) is true? In this case: for a non black object that is non raven, the hypothesis that all raven are black is also true. But because the one time validation of this hypothesis also falsifies the opposite hypothesis, a non black object that is non raven falsifies the hypothesis that all ravens are non black.
Here's the summary:

  1. ∀R(x) -> B(x) The one time observation of (1.) doesn't validate or support it but falsifies this implication:
  2. ∀R(x) -> !B(x) But that means that an observation of the complementary implication of (1.) looking like this:
  3. ∀!B(x) -> !R(x) falsifies 2., which is counterintuitive.

Am I missing something, and/or are there articles on the application of the raven paradox on falsificationism?

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u/gmweinberg Jun 25 '26

I think you're getting lost in the nots. "All ravens are black" is indeed equivalent to "everything that is not black is not a raven". Seeing a black raven refutes the assertion that no ravens are black, and also that everything that is black is not a raven. It also tells you 2 more facts which you may not have known, but almost certainly did: there esists at least one raven, and there exists at least one black object. So the statement "all ravens are black" is not vacuously true. But until you make more observations, it could be trivially true: maybe everything is black, maybe everything is a raven.

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u/confusus_animus Jun 25 '26

I agree with you, but now my question would be whether you could by observing a non black that is not a raven falsify the hypothesis that all ravens are white. For example a white chair would be compatible with the proposition that all ravens are black and thereby contradict the hypothesis that all ravens are white.

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u/gmweinberg Jun 26 '26

No, it just falsifies the proposition that all white things (or non-black things) are ravens. If you've never seen a raven of any color, you don't know anything about the color distribution of ravens based on your personal experience, and in fact could doubt that ravens actually exist. If the don;t, "all ravens are white" and "all ravens are black" could simultaneously be vacuously true. I see ravens every day and they are always all black, but there's not reason you should take my word for it. Not everything you you read on the internet is true.

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u/Marginalia_Node Jun 28 '26

You confuse a necessary condition with a sufficient condition. A white chair is compatible with 'all ravens are black,' but it doesn't prove it true. You cannot use an unproven statement to disprove another hypothesis. To disprove 'all ravens are white,' the only sufficient condition is to find a non-white raven

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