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PhilosophyTutor comments on A Parable On Obsolete Ideologies - Less Wrong
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Not even a rather bland carpenter who got slightly popular, enough for folks like Paul to make stuff up?
No, just as there is no evidence for Russell's teapot.
There is only one historical document from the time of Jesus' supposed life which even resembles evidence of a teacher called Jesus (or Yeshua or whatever), and that is just a reference to a rabbi with the right name who had one brother with the right name. Given that Jesus supposedly had four named brothers and multiple sisters, at least one of whom is also named, there's plenty of scope for that to be a false positive. Taking it as strong evidence would be like taking the discovery of a journalist named Clark who worked with a journalist named James in the 1920s as strong evidence that those two were the historical basis for the story of Superman.
There could have been a historical Yeshua so boring that none of his contemporaries, including the Romans, wrote anything about him during his life or for decades after he died. Or the character could have been entirely made up. Evidence to differentiate these two possible universes does not currently exist.
There are passages in Flavius Josephus that talk about him but are clear fakes. The untampered versions might have been about a real guy named Jesus, but more likely they were reports of Christians beliefs, or just nonexistent. I don't know of any other evidence for the existence of a carpenter turned rabbi who disliked Romans.
As the word evidence is commonly used, there is evidence for Russell's teapot -- just not evidence that you or me believe in. If someone says "Russell's teapot exists! I've seen it!", that is anecdotal evidence for its existence. Anything that suggests something is true or false is evidence, no matter how flawed that evidence may be.
It is by considering all the evidence, for and against our beliefs, that we progress towards truth.
I think I might have to write something specifically addressing this misconception because a few people seem to have picked it up.
It's only evidence for the existence of Russell's teapot if more people say they have seen it than you would expect in a universe where Russell's teapot does not exist.
(That's ignoring the fact that Russell's teapot is by stipulation non-observable and hence in that artificial situation we can skip Bayesian updating and just go straight to p=1 that anyone claiming to have observed it is lying or deluded).
I think our disagreement is to do with our differing usage of "evidence", not a misconception. I'd say that a sole anecdote of someone seeing Russell's teapot can be considered evidence for its existence, even though it's not credible evidence.
I would add that different situations require different standards of evidence, depending on how willing we are to accept false positives. The fire service only requires one phone call before they respond.
Perhaps a less abstract example would help. Uri Geller used to claim he was projecting his psychic powers over the TV or the radio and invite people to phone in if something "spooky" happened in their home. Inevitably people phoned in to report clocks stopping or starting, things falling off shelves and so on. It was pretty convincing stuff for people who believed in that sort of thing, but it turned out that when skeptics with no psychic powers whatsoever pretended to be psychic on the radio and invited people to phone in they got exactly the same flood of calls. Odd things happen all the time and if you get a large enough sample of people looking about the house for odd things to report you get a fair number of calls.
What would have been evidence for Uri Geller having psychic powers is if he got more calls than normal people when he did that stunt. Just getting the base rate of calls anyone else would proves nothing. As you said yourself, you have to look at all the evidence.
You might be thinking "I read this Bayes theorem essay, and it said evidence for X was whatever was more likely to be true in a universe where X was true. In a universe where Russell's teapot existed I'd be more likely to hear someone say they saw Russel's teapot, right? So it's evidence! Bayes says so". That line of reasoning only works if you don't have all the evidence to look at so you can't determine the base rate. If you can determine the base rate then it's probably going to turn out that the number of claimed teapot-sightings is consistent with the base rate of stupid noises humans make.
If all you have is the one anecdote then it does count as evidence, but only in a strictly philosophical or mathematical sense. Not in any practical sense though since the shift in the relevant p value isn't going to be visible in the first twenty or thirty decimal places and I doubt anyone alive has that level of precision in their decision-making. (The odds of someone having seen Russell's teapot could be said, very conservatively, to be lower than the odds of someone winning the lotto twice in a row).
I don't think a less abstract example will solve a dispute over word usage.
And even if they did receive a statistically significant number of calls, perhaps people lied, grouped together and phoned in supernatural events that hadn't actually occurred.
I don't have a problem with dismissing evidence if it truly is highly irrelevant. I think the problem is that in some cases evidence that at first seems irrelevant turns out to be important.
How relevant a piece of evidence truly is might not become apparent even after significant consideration. This is why, for important matters, I explore as much evidence as possible, even the seemingly irrelevant evidence.
This is really a dispute over maths. The laws of probability are the law, they don't depend on word usage.
Of course people can mock up evidence of things that are not in fact true. It's still evidence from the perspective of people who are not in on the plot. All of our evidence for everything could in theory have been mocked up by the architects of the Matrix and it would still all be evidence, from our perspective.
I'm not clear how this is relevant to the base rate fallacy though.
Strictly speaking what's going on there is that you are collecting facts which might later turn out to be evidence for a hypothesis you have not articulated yet. This is an entirely rational approach to solving certain classes of problems. It doesn't change the definition of evidence though,
Explaining the way one uses a word isn't a statement about maths or the laws of probability either.
It's not. I was riffing on what you said.
I was discussing ascertaining the trustworthiness of evidence concerning a hypothesis you are currently considering. Like an investigation into whether Uri Gellers phone calls were genuine reports of supernatural events, for example.
Of course not. I'm not trying to suggest that my usage of "evidence" is somehow better or superior than yours. I do think mine is more common, but that's a matter of opinion.
It is, actually. It's the Bayesian definition that evidence for X is something more likely to be true in a universe where X than in a universe where -X.
Part of the point of Bayes' Theorem is that correction for the base rate fallacy is baked in. That's a large part of what separates Bayesian rationality from irrationality,
But nobody is saying that... er, right?