It's definitely the first. The second is bizarre. The third can be steelmanned as "Given my evidence, an ideal thinker would estimate the probability to be 20%, and we all here have approximately the same evidence, so we all should have 20% probabilities", which is almost the same as the first.

It's definitely the first. The second is bizarre. The third can be steelmanned as "Given my evidence, an ideal thinker would estimate the probability to be 20%, and we all here have approximately the same evidence, so we all should have 20% probabilities", which is almost the same as the first.