Poignant short story about truth-seeking that I just found. Quote:

"No," interjected an internal voice. "You need to prove that your dad will appear by a direct argument from the length of your nails, one that does not invoke your subsisting in a dream state as an intermediate step."

"Nonsense," retorted another voice. "That we find ourselves in a dream state was never assumed; rather, it follows so straightforwardly from the long-nail counterfactual that the derivation could be done, I think, even in an extremely weak system of inference."

The full thing reads like a flash tour of OB/LW, except it was written in 2001.