There is a distinction between the epistemic question of how best to form beliefs, and the dialectical question of how best to present them as claims. "Claims" are dialectical offerings, not simply logical propositions nor epistemic beliefs. I suppose one *could* internalize the process of offering such, just as one *could* talk to oneself. But I don't see how that affects my point. We are still projecting an audience that is to be convinced, and asking under what circumstances one could expect such an audience to be thus convinced.
Heh, no, I wasn't referring to Crusoe gone lonesome and conjuring up Friday to speak to, or that Life of Pi kid conjuring up a tiger at sea to converse with.
I think it makes sense to think of the burden of proof vesting with propositions, or claims, rather than people. Whichever proposition, whichever claim, satisfies the burden of proof; that proposition, that claim, it is reasonable to accept.
As for who is to actually go look for the proof, well, that would be whoever gives a damn.
Sure, in daily interactions, should someone present a claim, we do ask them for proof, or evidence. But I think that's an approximation of and shorthand for "You're selling me that claim, so presumably you've bought it yourself; and you can only have reasonably bought it yourself if you've seen adequate proof or evidence for it; plus you're going to the trouble of selling me it so presumably you can be expected to also take the trouble to show me the proof, that in any case you presumably already have. So, yeah, show me the proof, else walk away with your claim, because I'll assume that's random nonsense that had no evidence supporting it."
That approximation works well enough in practice, in general. But one can easily think up scenarios where a claim is presented, and the one who actually takes the trouble to see if there's evidence for it is someone to whom the claim is important, not necessarily the one who presented it. That is because burden of proof attaches to propositions, not people.
Rationality, I believe, is primarily about how to think reasonably; and also about how to interact with others, sure, but that latter I'd say is secondary. It isn't as if rationality only obtains in a group, or by a solitary man projecting and/or hallucinating other people to talk with.
