This is all fine and good, but it does not address what “evidence” is. I cannot gather evidence of extra solar planets (either evidence for or against existence) with my naked eyes. So in this experiment, even though I see no “evidence” of extra solar planets by looking up into the sky, I still do not have evidence of absense, because in fact I have no evidence at all.
Evidence, from the aspect of probability theory, is only meaningful when the experiment is able to differential between existence and absence.
Then the real question becomes: do we have evidence that our experiment is able to yield evidence? And the only way to prove this to the affirmative, is to find something. You cannot know you experiment is designed correctly.
The fact that you can’t see them when you look outside is evidence against their presence, it’s just extremely weak evidence. See also the Raven paradox.
But it’s completely unamazing how many people will interpret “evidence” as “strong enough evidence to be worth taking notice of”, because that is how the word is actually used outside circumscribed mathematical contexts.
Right, and in fact the very idea of “extremely weak evidence” is really only worth paying attention to because it resolves various seeming paradoxes of evidence, such as the extrasolar planets and raven problems above.
Yup. To be honest, it’s not actually that amazing that it’s interpreted as “strong evidence”, or “this thing is probably true”, because arguments are soldiers and all that.
It’s not about arguments being soldiers, but basic Gricean maxims. In everyday talk you don’t call something “evidence” unless it actually matters that it is evidence, and it only matters if it is strong enough to be worth attending to.
Just because there is this other, mathematically defined concept called “evidence”, according to which every purple M&M is evidence for the blackness and whiteness of crows, you don’t get to say that everyone else is wrong for not using the word the way you redefined it. Instead, you must recognise that this is a different concept, called by the same name, and take care to distinguish the two meanings.
What next, insisting that black paint isn’t black?
It’s always better to rename overloaded terms, or at least to make clear which meaning (the colloquial or the technical) one defaults to. Quibbling over what to name which doesn’t solve any issues and is mostly just kicking the can down the road, but allow me to say that if there’s one place on which I always default to the technical definition, it’s LW. Where else if not here?
I understand that the LW fraction which aims to prioritize accessibility and strives to avoid jargon, may also strive to avoid counter-intuitive technical definitions for the sake of commonly used interpretations. I just don’t subscribe to their methods.
Sorry, I wasn’t clear. I agree that it’s reasonable, except when discussing prob. math, to assume “evidence” means “evidence worth mentioning”. I noted that, while not “reasonable” exactly, it’s even natural that it tends to be interpreted as “this is my side, I offer evidence in tribute”, from an evopsych perspective :/
There is another way: Look really really hard with tools that would be expected to work. If you find something? Yay, your hypothesis is confirmed. If you don’t? You’d better start doubting your hypothesis.
You already do this in many situations I’m sure. If someone said, “You have a million dollars!” and you looked in your pockets, your bank accounts, your stock accounts (if any), etc. and didn’t find a million dollars in them (or collectively in all of them put together), you would be pretty well convinced that the million dollars you allegedly have doesn’t exist. (In fact, depending on your current economic status you might have a very low prior in the first place; I know I would.)
Really, the issue here is whether evidence has to increase probability (of existence or nonexistence) by a positive amount or a non-negative amount. The difference between those two sets is the very important “zero.”
You are interested in the question: “Are there extra-solar planets?”, with possibilities “Yes” and “No”. You wonder how to answer the question, and decide to try the experiment “look with my naked eyes.” You sensibly decide that if you can see any extra-solar planets, then it’s not less likely that there are extra-solar planets, and if you can’t see extra-solar planets, then it’s not more likely that there are extra-solar planets. The strength of those effects is determined by the quality of the experiment; in this case, that strength is 0.
The specific fallacy in question is saying that all outcomes of an experiment make a claim more likely- that is inconsistent with how probability works. Similarly, one can argue that you should have a good estimate of the quality of an experiment before you get the results. That estimate doesn’t have to be perfect- you can look at the results and say “I’m going to doublecheck to make sure I didn’t screw up the experiment”- but changing your bet after you lose should not be allowed.
This is all fine and good, but it does not address what “evidence” is. I cannot gather evidence of extra solar planets (either evidence for or against existence) with my naked eyes. So in this experiment, even though I see no “evidence” of extra solar planets by looking up into the sky, I still do not have evidence of absense, because in fact I have no evidence at all.
Evidence, from the aspect of probability theory, is only meaningful when the experiment is able to differential between existence and absence.
Then the real question becomes: do we have evidence that our experiment is able to yield evidence? And the only way to prove this to the affirmative, is to find something. You cannot know you experiment is designed correctly.
The fact that you can’t see them when you look outside is evidence against their presence, it’s just extremely weak evidence. See also the Raven paradox.
To be fair, it’s amazing how people will interpret “evidence” as “strong evidence”.
But it’s completely unamazing how many people will interpret “evidence” as “strong enough evidence to be worth taking notice of”, because that is how the word is actually used outside circumscribed mathematical contexts.
Right, and in fact the very idea of “extremely weak evidence” is really only worth paying attention to because it resolves various seeming paradoxes of evidence, such as the extrasolar planets and raven problems above.
Yup. To be honest, it’s not actually that amazing that it’s interpreted as “strong evidence”, or “this thing is probably true”, because arguments are soldiers and all that.
It’s not about arguments being soldiers, but basic Gricean maxims. In everyday talk you don’t call something “evidence” unless it actually matters that it is evidence, and it only matters if it is strong enough to be worth attending to.
Just because there is this other, mathematically defined concept called “evidence”, according to which every purple M&M is evidence for the blackness and whiteness of crows, you don’t get to say that everyone else is wrong for not using the word the way you redefined it. Instead, you must recognise that this is a different concept, called by the same name, and take care to distinguish the two meanings.
What next, insisting that black paint isn’t black?
It’s always better to rename overloaded terms, or at least to make clear which meaning (the colloquial or the technical) one defaults to. Quibbling over what to name which doesn’t solve any issues and is mostly just kicking the can down the road, but allow me to say that if there’s one place on which I always default to the technical definition, it’s LW. Where else if not here?
I understand that the LW fraction which aims to prioritize accessibility and strives to avoid jargon, may also strive to avoid counter-intuitive technical definitions for the sake of commonly used interpretations. I just don’t subscribe to their methods.
Sorry, I wasn’t clear. I agree that it’s reasonable, except when discussing prob. math, to assume “evidence” means “evidence worth mentioning”. I noted that, while not “reasonable” exactly, it’s even natural that it tends to be interpreted as “this is my side, I offer evidence in tribute”, from an evopsych perspective :/
There is another way: Look really really hard with tools that would be expected to work. If you find something? Yay, your hypothesis is confirmed. If you don’t? You’d better start doubting your hypothesis.
You already do this in many situations I’m sure. If someone said, “You have a million dollars!” and you looked in your pockets, your bank accounts, your stock accounts (if any), etc. and didn’t find a million dollars in them (or collectively in all of them put together), you would be pretty well convinced that the million dollars you allegedly have doesn’t exist. (In fact, depending on your current economic status you might have a very low prior in the first place; I know I would.)
Really, the issue here is whether evidence has to increase probability (of existence or nonexistence) by a positive amount or a non-negative amount. The difference between those two sets is the very important “zero.”
You are interested in the question: “Are there extra-solar planets?”, with possibilities “Yes” and “No”. You wonder how to answer the question, and decide to try the experiment “look with my naked eyes.” You sensibly decide that if you can see any extra-solar planets, then it’s not less likely that there are extra-solar planets, and if you can’t see extra-solar planets, then it’s not more likely that there are extra-solar planets. The strength of those effects is determined by the quality of the experiment; in this case, that strength is 0.
The specific fallacy in question is saying that all outcomes of an experiment make a claim more likely- that is inconsistent with how probability works. Similarly, one can argue that you should have a good estimate of the quality of an experiment before you get the results. That estimate doesn’t have to be perfect- you can look at the results and say “I’m going to doublecheck to make sure I didn’t screw up the experiment”- but changing your bet after you lose should not be allowed.