Not all evidence of (2) is evidence of (1). (1) and (2) are formally equivalent. 'Evidence' is a matter of fact.
A green apple is evidence in support of (2) in terms of matters of fact. It is not evidence in support of (1) in terms of matters of fact. — quine
I said that 'evidence' is a tricky expression. Evidence is not related to formalization. Equivalence is about formalization. Evidence is about matters of fact. The paradox suggested above is a mixture of two different kinds of issues. '(1) and (2) are logically equivalent' - It's about formalization. 'Evidence of (2) supports evidence of (1)' - It's about matters of fact. — quine
(2*) For every x, if x is not black, then x is not a raven.
Do you see that 'a green apple' is not related to (2*)?
— quine
No. Green apples are evidence that support this claim. They're not black and not ravens. — Michael
What's even more annoying is that intuition seems to say that a black raven is not evidence that non-black things are non ravens. — unenlightened
Back in the day, 'all' statements had no existential import, whereas 'some' statements did. Following which, one might have a bit of a get out, by denying that evidence can be for universal statements, but only against. Thus we have evidence above against all ravens being black and for 'some ravens are white'.
Thus 'all dragons breathe fire' cannot be supported by any number of fire breathing dragons, but is falsified by a single non-fire-breathing dragon. This fits with the Venn diagram approach, and also with Popper. — unenlightened
If that were the case then much of science would have to be dismissed. From a finite number of observations we infer general rules of nature that are applicable to everything of that type. — Michael
I don't think so. You just have to preface your universals with 'As far as I know', or some such trope. — unenlightened
The evidence that as far as I know all ravens are black is limited to my having seen some ravens and them all being black. — unenlightened
(1) All ravens are black. — Michael
The green apples are not evidence that there are ravens of any stripe. — unenlightened
They're logically equivalent. Therefore evidence that supports the truth of one ipso facto supports the truth of the other. — Michael
What would the argument be for that? — Terrapin Station
evidence for one is evidence for the other because they're logically equivalent. — Michael
Prima facie, it seems to be no evidence at all, since the claim is universal, and a single datum doesn't help us with the universal. — andrewk
That can't be the argument for why evidence for one is evidence for the other just in case they're logically equivalent. After all, it's just a restatement of what it's supposed to be an argument for. — Terrapin Station
I'm pretty sure it's axiomatic — Michael
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