Zephan: What is Evidence?

The question is "what comprises evidence?" is an interesting conundrum in the non-legal sense as well (Hempel's paradox).If we consider the statement:All swans are blackHow could we prove, or at the very least provide evidence for this? One way would be to go round observing swans, and every black swan we saw would be additional evidence towards the proposition, whereas if we saw a blue, or a red swan, this would disprove the proposition immediately, despite all the "evidence".But I can't be bothered to do this. Instead I take the logically equivalent proposition:All things that are not black are not swansAnd set about confirming this by looking around me. There's a blue pen here, so that is (weak) evidence for my proposition - in fact, I can find thousands, if not millions, of non-black objects here, none of them swans, so, given the above, do my observations then constitute strong "evidence" of my initial claim?It obviously doesn't since each "non-black" observation only collapses the total possibilities by an infinitesimal amount (although if you lived on a hypothetical distant planet where everything around you was, in fact, a black swan, would this mean that the appearance of a blue pen was then strong evidence for the proposition? No idea )The paradox comes in by the fact that the blue pen can be used to confirm the proposition that "all swans are black" and "all swans are white" simultaneously.In summary then, my first approximation is that evidence for a proposition is "sufficient" information (in the Shannon sense) which excludes alternative possibilities.{Or alternatively, what evidence is NOT is NOT "sufficient" information (in the Shannon sense) which excludes alternative possibilities. }PE

There is an implicit assumption of time invariance in the laws of physics, as well as invariance in space. Obviously, you can't "prove prove" this assumption, but you can disprove it - and its stood up to any test so far.That said, the laws of physics could change tomorrow, in much the same way as the sky could fall on our heads tomorrow. I don't see anything wrong in the scientific method for the approach it must necessarily take in its assumptions.

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Another cool thing is that since the 'blue pen' can prove both a statement and it's opposite, it is irrelevant to the statement. It can't exclude the statement's alternative possiblities so it's not a valid premise

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I like this idea and want to develop it further - what if you were asked to discern between two contradictory premises:1) All swans are blue
2) All swans are black
?Does this then imply that my finding a blue pen is *not* irrelevant, given that this can only provide "supporting evidence" for 2) and not 1)?PE

BG,Its difficult to see where (or even if) we diverge. I don't think thats quite what I was saying. To spell it out:Premise 1: All swans are blue
i.e
Premise 1a: All not-blue things are not swansis trueORPremise 2: All swans are black
i.e
Premise 2a: All not-black things are not swansis true.A blue pen can only be used as supporting evidence (not a conclusion, by any means) for 2a (and by implication for 2), and not for 1a - so its not entirely irrelevant in this context despite your previous statement that: although *common sense* would seem to suggest that the blue pen was utterly irrelevant.I'm sure I saw a good rebuttal of this paradox somewhere, I'll see if I can dig it oot...PE