And when X = [the sky is blue], you shouldn’t decrease the weight of evidence you assign to X at all, because the statement was never evidence of that in the first place: it’s just remarking on something obvious.
It’s still evidence; it’s more likely conditional on the sky being blue than conditional on the sky not being blue. But the weight of one remark is very weak evidence compared to that which is already available to you.
If everyone started asserting that the sky was green, that it had always been green, and that you must be delusional for remembering otherwise, you might be wiser to doubt the input of your own senses.
Although if you’re questioning your own sanity, I suppose it might be likelier that you’re imagining that everyone has started claiming that the sky is green than that you’re imagining that it’s blue and that people ever used to say so.
And this reminds me of a post a while back about the reliability of peer-reviewed science journals over your own senses. (The catch being that you can’t extract information from science journals without using your senses.)
It’s still evidence; it’s more likely conditional on the sky being blue than conditional on the sky not being blue. But the weight of one remark is very weak evidence compared to that which is already available to you.
If everyone started asserting that the sky was green, that it had always been green, and that you must be delusional for remembering otherwise, you might be wiser to doubt the input of your own senses.
Although if you’re questioning your own sanity, I suppose it might be likelier that you’re imagining that everyone has started claiming that the sky is green than that you’re imagining that it’s blue and that people ever used to say so.
Okay, maybe “at all” was an exaggeration.
And this reminds me of a post a while back about the reliability of peer-reviewed science journals over your own senses. (The catch being that you can’t extract information from science journals without using your senses.)