Two Kinds of Minds
I essentially believe that if you are a Boltzmann brain, then your "world" is as real as the one we inhabit. Or another way of putting it is, "reality" is not a function of some kind of metaphysical existence, it's a function of the reliability of information. Water is real because I've experienced it before and I will experience it again, and it can be expected to follow certain laws at all times. It doesn't matter whether there is really such a thing as water, or whether I'm hallucinating. What matters is that the thing that I observe and call "water" behaves as if it is real (if it is a hallucination, it is a persistent and predictable one). The Boltzmann brain may or may not experience anything as "real" as the water I experience, but if it does, then that water is perfectly real for the brain's purposes.
So far so good. But what do we make of analytic truth, and the fact that reality seems to conform closely to it? After all, these things don't have to be true in a dream. So why would they have to be true to a Boltzmann brain?
You might say that analytic truth and certain kinds of inductive truth have to hold because they are the preconditions for rational thought. (I understand this to be an argument that Kant made, though I haven't read his version of it.) But again, this only seems to be true if the mind is bound by the laws of the world it observes. That has to be the case for a brain that evolves within a world like ours, but I don't see why it has to be true of a Boltzmann brain. Sure, the universe giving rise to the Boltzmann brain may need to obey certain physical laws, but why would the universe observed by the Boltzmann brain be bound by those laws, or any others? Would it really remove the conditions for rational thought if there were a little "magic" in the world?
So we can divide minds into two types: those whose perceived worlds include their own brains, and those whose perceived worlds don't. But you don't necessarily know which type of mind you are. Our organic brains seem to be of the first type, and in fact maybe there is a good argument that any mind that observes an orderly world with neat correspondences between observation and analytical truth must be the first type of mind. But I haven't fully figured this out, I am just thinking it through. One implication I wonder about is whether the singularity will mark a transition from one type of mind to another, since there is no particular reason that synthetic minds would need to be bound by the constraints imposed by our natural laws and analytical truth. On the other hand, maybe that is a desirable feature. On the third hand, maybe it is a computationally expensive feature that will have to be abandoned!
I've gotten to the point where I'm not sure I'm making any sense whatsoever, which means it's time to click "publish" on this blog post.