Take the ultimate macrocosm of the ultimate reality, whatever it might be. Let's call it the "Objective World" (henceforth, OW). Now, the OW is of such a depth that we can identify and focus on various microcosms, little worlds in themselves. Each of these microcosms will in turn contain further mini-worlds, ad infinitum. Human reflection has an infinite zoom, and can choose to focus on any particular "world" - we are not restricted to the OW. All of these worlds are (at least in a certain respect) real. They are simply different ways of looking at a single reality. A different frame of reference, if you will.
My central theses are that:
- truth is relative to the 'world of reference' [It should be noted, however, that all micro-worlds are ultimately reducible to the OW... but such a reduction will often require significant semantic alterations in order to preserve the truth values of attributed propositions.]
- The 'world of reference' will vary according to context.
That was a rather abstract introduction. So let's consider a simple example: a fictional story. I'm suggesting that the imaginary world communicated by the story is (in a sense) real. One can say things like "Frodo went to Mt Doom to destroy the One Ring", and it is true within the context of Tolkien's world, despite its apparent literal falsity. The method of reduction in this case should be obvious: propositions about Tolkien's world simply need to be 'translated' into propositions about what Tolkien wrote in his famous books. Fictional worlds are reducible to real-world text on real-world pages.
The example I borrowed from Patrick may help you to get an intuitive grasp of this theory:
Suppose I say to you “In my dream last night, I was walking down the street-”, it is clearly inappropriate to respond “Liar! You were lying in bed asleep!”. Instead, we implicitly recognise that the phrase “In my dream last night” alerts the listener to a shift of semantic context: the truth of the subsequent proposition is to be evaluated in terms of the dream world, not the real world.
So that should give you the basic idea. Hopefully this theory of metaphysical contextualism will strike you as intuitively plausible - perhaps even obvious. What really makes it useful, however, is the response it allows us to give to the Skeptic. I discussed this in my post on Skepticism & the Matrix (but note that what I previously referred to as the "Real World (RW)", is what I'm now calling the "OW", since the microcosmic worlds are - in a sense - no less real).
The Skeptic highlights the distinction between the world we commonly assume to be reality (CW), and what is in fact the ultimate OW (which we cannot possibly know). A common scenario is to suggest that you might be a brain in a vat (BIV), being ‘fed’ experiences by a super-computer which electrically stimulates your brain, causing lucid hallucinations which you have mistaken for reality. In this case, our CW is reducible to the rules of the computer program that determines the experiences fed to a BIV in any given situation.
I am suggesting here that even though you are a (handless) BIV in the OW, it is nevertheless true that you have two hands - within the context of the CW. The semantic revision I propose to achieve this is roughly similar to that of Hilary Putnam (in Brains in a Vat) who suggests that a BIV saying “there is a tree in front of me” likely speaks the truth, given what “tree” and “in front of” mean in Vat-English. I suggest that when someone says "I have two hands", what they really mean is "I have two hands in the CW", rather than "I have two hands in the OW". We can know the former proposition to be true, despite our ignorance of the latter.
But enough about Skepticism. My main purpose here was to expand the theory from the mere delineation of CW from OW, to instead allow us to choose from infinitely many reference frames. I can talk about the world of a dream, of a story, of my conscious experiences, of a computer simulation, of interstellar interactions, or of anthills. Some propositions will be true in some of these worlds, but not others. Nevertheless all those worlds are in some sense real, because they can all be 'reduced' to the OW. The microworlds supervene on the macroworld. They just look at reality from different perspectives.
Update: Some helpful folks at Ephilosopher inform me that the name "semantic contextualism" is already used to refer to a certain variant of epistemological contextualism. To emphasise the idea that there are multiple 'worlds' or perspectives on reality, I'll rename my theory here as "Metaphysical contextualism" instead.