Alone in my office, it can seem reasonable to me to have only about a 99% to 99.9% credence that the world is more or less how I think it is, while reserving the remaining 0.1% to 1% credence for the possibility that some radically skeptical scenario obtains (such as that this is a dream or that I'm in a short term sim).
But in public... hm. It seems an odd thing to say aloud to someone else! The question rises acutely as I prepare to give a talk on 1% Skepticism at University of Miami this Friday. Can I face an audience and say, "Well, I think there's a small chance that I'm dreaming right now"? Such an utterance seems even stranger than the run-of-the-mill strangeness of dream skepticism in solitary moments.
I've tried it on my teenage son. He knows my arguments for 1% skepticism. One day, driving him to school, a propos of nothing, I said, "I'm almost certain that you exist." A joke, of course. How could he have heard it, or how could I have meant it, in any other way?
One possible source of strangeness is this: My audience knows that they are not just my dream-figures. So it's tempting to say that in some sense they know that my doubts are misplaced.
But in non-skeptical cases, we can view people as reasonable in having non-zero credence in propositions we know to be false, if we recognize an informational asymmetry. The blackjack dealer who knows she has a 20 doesn't think the player a fool for standing on a 19. Even if the dealer sincerely tells the player she has a 20, she might think the player reasonable to say he has some doubt about the truth of the dealer's testimony. So why do radically skeptical cases seem different?
One possible clue is this: It doesn't seem wrong in quite the same way to say "I think that we might all be part of a short-term sim". Being together in skeptical doubt seems fine -- in the right context, it might even be kind of friendly, kind of fun.
Maybe, then, the issue is a matter of respect -- a matter of treating one's interlocutor as an equal partner, metaphysically and epistemically? There's something offensive, perhaps, or inegalitarian, or oppressive, or silencing, about saying "I know for sure that I exist, but I have some doubts about whether you do".
I feel the problem most keenly in the presence of the people I love. I can't doubt that we are in this world together. It seems wrong -- merely a pose, possibly an offensive pose -- to say to my seriously ill father, in seeming sincerity at the end of a philosophical discussion about death and God, "I think there's a 99.8% chance that you exist". It throws a wall up between us.
Or can it be done in a different way? Maybe I could say: "Here, you should doubt me. And I too will doubt you, just a tiny bit, so we are doubting together. Very likely, the world exists just as we think it does; or even if it doesn't, even if nothing exists beyond this room, still I am more sure of you than I am of almost anything else."
There is a risk in radical skepticism, a risk that I will doubt others dismissively or disrespectfully, alienating myself from them. But I believe that this risk can be managed, maybe even reversed: In confessing my skepticism to you, I make myself vulnerable. I show you my weird, nerdy doubts, which you might laugh at, or dismiss, or join me in. If you join me, or even just engage me seriously, we will have connected in a way that I treasure.