I've been traveling in Spain and France, and it has been hard to find the time to pull together a full-length post. But this thought struck me a few nights ago, when I probably should have been paying closer attention to the dinner conversation: What would happen to Berkeleyan metaphysics if we swapped his monotheism for polytheism?
George Berkeley, you will recall, is an 18th-century philosopher who held that matter doesn't exist, only immaterial souls and their experiences. Your computer screen? Just an idea in your immaterial soul. Your fingers on the keyboard? Just ideas in your immaterial soul. The human brain, as seen by a neurosurgeon? Again, just an idea in the surgeon's immaterial soul. Behind these ideas are not physical substances but rather the will of God, who ensures that your sensory experiences are all nicely coordinated with each other and with the sensory experiences of other people. God ensures -- since He loves order so very much! -- that when I have an experience of seeing a red dot here and then I experience willing my eyes to move to the left I then have a sensory experience of the dot as shifting rightward in my visual field. He ensures that you and I, who experience each other as being in the same room, also have similar sensory experiences of that room, allowing for variation in perspective. Etc. It's like a very well-coordinated mutual dream. The Matrix is tame compared to Berkeley.
Berkeley, being a good Christian, believed in a single, perfect God, but what if we tweaked Berkeley's view, allowing for a limited God? What if sometimes God fell into inconsistencies, so that when you and I experience ourselves as being in the same room, sometimes I see one thing written on the board (the letter P) and you see something else (the letter Q)? God could try to cover up this error, so that when I say "I see a 'P' on the board" you hear my words as "I see a 'Q' on the board". But such cover-ups could multiply vastly: I write 'P' in my notebook, you write 'Q', then we both share our notebooks with some third party.... In the extreme, we might have to splinter off into entirely separate worlds.
Or maybe God could do a late correction: What I was seeing as 'P', I now see as 'Q', consistently with you -- and then presumably (unless God also alters my memory) I attribute my error to initial misperception. If God showed predictable patterns in such errors, maybe we could study such errors under the heading of "perceptual illusions" and see nothing so strange in them.
We might alternatively imagine more than one god, with competing goals. Without an objective physical reality to constrain them, the gods might create experiences in their followers that would be "physically inconsistent" with the experiences in other gods' followers. Perhaps God A allows his followers to experience refreshing rain after the rain dance, while God B's followers experience the scene of watching the physical bodies of the exact same followers of God A dancing for rain and being rewarded with only a dry spell. Maybe the two sects go to war and when Person X dies, the followers of God A experience X's demise as glorious bravery, while the followers of God B see X dying the death of a fleeing coward. (Person X himself presumably either willed to fight or to flee, but the others in the battle don't see his will, instead only having the visual experiences that their god chooses to deliver to them.)
Philosopher of science Thomas Kuhn says that scientists with different theories literally "live in different worlds" because their sensory experiences and their recorded data are transformed by their theoretical commitments. This is perhaps just a more radical version of that idea.
Okay, so it's not very plausible, if we're interested in the metaphysical truth of things! But maybe it's more interesting than hearing about the Barcelona-Madrid football match, if you're sitting in a restaurant full of Spaniards. Or maybe it was a side-effect of the fish.