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.
This sounds like scientism.
Because I have experience with good rationalists, and the kind of people they have relationships with, and I am a bayesian so I can assign degrees of belief to propositions that I haven't tested directly. In this case, it seems reasonable that similar people have similar relationship-behaviors, and so my existing knowledge is relevant.
Rather like "how do you know that the fastest dog in the world can't outrun a formula one car?" - I know this with high certainty because I believe that similar animals behave in similar ways.