In Epicurus's letter to Pythocles, he proposes three different explanations for lightning strikes: compression of air by wind, a cloud suddenly breaking, or a buildup of fire suddenly bursting.
All wrong, but he goes on to say (Makridis translation):
It is indeed possible that the thunderbolt may be generated in any one of many more ways.
Maybe this is all you need if you're annoyed with people saying it's Zeus's wrath so you'd better make sacrifices at their temple.
You just have to say, well, it could be a lot of other things too.
Meeting unfounded explanations with more explanations
I used to think you shouldn't propose explanations without evidence.
Now I think you should have at least three.
If you come up with an explanation that's total speculation or pseudoscience, don't feel bad for making unfounded claims.
Think of two more.
Or if someone else proposes some bullshit explanation, it's more fun to come up with new explanations than to complain about a lack of evidence.
But more importantly, that's what it means to lack evidence, right?
We know there's no evidence when we can propose alternatives, and there's no evidence that falsifies them.
I do sometimes propose alternatives adversarially, when I'm annoyed, as Epicurus was, at the unfounded claims of others.
When I say you lack evidence, the content of my claim is that you cannot rule out other plausible alternatives.
The right way to make that case, at least in my opinion, is directly: list the alternatives.
Everything else (you haven't done a study, or you did a study but it wasn't randomized, etc.) is at best a proxy for this substance.
But, again, it's fun to propose explanations.
When someone isn't taking what they're saying too seriously, I think I should meet them in the same spirit and play the same game.
Recognizing evidence by the possibilities it excludes
Of course, sometimes a claim is well-founded after all.
Epicurus was not always able to notice well-supported claims.
His letter to Pythocles looks great as long as he's talking about weather phenomena like lightning.
But it looks bad whenever it touches on astronomy, which was impressive even in his time.
For example, Epicurus says that maybe the moon has its own light, and maybe it reflects the light of the sun.
Reasonable, right?
But if it's reflected sunlight, then the illuminated part of the moon should always be facing the sun.
And it is; an enormous unexplained coincidence if the moon is just glowing.
Not only did the ancient Greek astronomers know that the moon was reflecting sunlight, but within a generation Aristarchus was able to determine, from the pattern of illumination, that the sun must be much farther from us than the moon.
Since they appear the same size in the sky, the sun must therefore be much larger.
Steven Weinberg's To Explain the World has a great explanation of the argument.
Epicurus says that we shouldn't let ourselves be intimidated by astronomers.
And, sure, we shouldn't listen to someone just because they do fancy math.
But the ancient Greek astronomers had the real thing: observations that perfectly fit one possibility but not another.
But I still think the ensemble of explanations was the right place to start.
That's what evidence is: it's what rules out the other explanations.
The best way to see that you have evidence is to see the alternatives that the evidence falsifies.
Every other standard of evidence is just a proxy.
In Epicurus's letter to Pythocles, he proposes three different explanations for lightning strikes: compression of air by wind, a cloud suddenly breaking, or a buildup of fire suddenly bursting.
All wrong, but he goes on to say (Makridis translation):
Maybe this is all you need if you're annoyed with people saying it's Zeus's wrath so you'd better make sacrifices at their temple. You just have to say, well, it could be a lot of other things too.
Meeting unfounded explanations with more explanations
I used to think you shouldn't propose explanations without evidence. Now I think you should have at least three. If you come up with an explanation that's total speculation or pseudoscience, don't feel bad for making unfounded claims. Think of two more.
Or if someone else proposes some bullshit explanation, it's more fun to come up with new explanations than to complain about a lack of evidence. But more importantly, that's what it means to lack evidence, right? We know there's no evidence when we can propose alternatives, and there's no evidence that falsifies them.
I do sometimes propose alternatives adversarially, when I'm annoyed, as Epicurus was, at the unfounded claims of others. When I say you lack evidence, the content of my claim is that you cannot rule out other plausible alternatives. The right way to make that case, at least in my opinion, is directly: list the alternatives. Everything else (you haven't done a study, or you did a study but it wasn't randomized, etc.) is at best a proxy for this substance.
But, again, it's fun to propose explanations. When someone isn't taking what they're saying too seriously, I think I should meet them in the same spirit and play the same game.
Recognizing evidence by the possibilities it excludes
Of course, sometimes a claim is well-founded after all.
Epicurus was not always able to notice well-supported claims. His letter to Pythocles looks great as long as he's talking about weather phenomena like lightning. But it looks bad whenever it touches on astronomy, which was impressive even in his time.
For example, Epicurus says that maybe the moon has its own light, and maybe it reflects the light of the sun. Reasonable, right? But if it's reflected sunlight, then the illuminated part of the moon should always be facing the sun. And it is; an enormous unexplained coincidence if the moon is just glowing.
Not only did the ancient Greek astronomers know that the moon was reflecting sunlight, but within a generation Aristarchus was able to determine, from the pattern of illumination, that the sun must be much farther from us than the moon. Since they appear the same size in the sky, the sun must therefore be much larger. Steven Weinberg's To Explain the World has a great explanation of the argument.
Epicurus says that we shouldn't let ourselves be intimidated by astronomers. And, sure, we shouldn't listen to someone just because they do fancy math. But the ancient Greek astronomers had the real thing: observations that perfectly fit one possibility but not another.
But I still think the ensemble of explanations was the right place to start. That's what evidence is: it's what rules out the other explanations. The best way to see that you have evidence is to see the alternatives that the evidence falsifies. Every other standard of evidence is just a proxy.