The question “how would the coin have landed if I had guessed tails?” seems to me like a reasonably well-defined physical question about how accurately you can flip a coin without having the result be affected by random noise such as someone saying “heads” or “tails” (as well as quantum fluctuations). It’s not clear to me what the answer to this question is, though I would guess that the coin’s counterfactual probability of landing heads is somewhere strictly between 0% and 50%.

I agree that is is a well-defined question, though not easily answered without knowing how guessing physically affects flipping the coin, reading the results (humans are notoriously prone to making mistakes like that) and so on. But I suspect that Nisan is asking something else, though I am not quite sure what. The post says

In real life, we have a causal model of the world that tells us that the first counterfactual is correct. But we don’t have anything like that for logical uncertainty; the best we have is logical induction, which just give us a joint distribution.

I am not sure how physical uncertainty is different from logical uncertainty, maybe there are some standard examples there that could help the uninitiated like myself.

The question “how would the coin have landed if I had guessed tails?” seems to me like a reasonably well-defined physical question about how accurately you can flip a coin without having the result be affected by random noise such as someone saying “heads” or “tails” (as well as quantum fluctuations). It’s not clear to me what the answer to this question is, though I would guess that the coin’s counterfactual probability of landing heads is somewhere strictly between 0% and 50%.

Oh, interesting. Would your interpretation be different if the guess occurred well after the coinflip (but before we get to see the coinflip)?

Sure, in that case there is a 0% counterfactual chance of heads, your words aren’t going to flip the coin.

Ok. I think that’s the way I should have written it, then.

I agree that is is a well-defined question, though not easily answered without knowing how guessing physically affects flipping the coin, reading the results (humans are notoriously prone to making mistakes like that) and so on. But I suspect that Nisan is asking something else, though I am not quite sure what. The post says

I am not sure how physical uncertainty is different from logical uncertainty, maybe there are some standard examples there that could help the uninitiated like myself.