Wednesday, February 27, 2008

what i'm studying this semester.

i'm taking a seminar on modal realism, a theory devised by the great analytic metaphysician david lewis. i don't know that much about metaphysics-- my primary goal this semester, school-wise, is to learn a heck of a lot more-- so while i'm about to take a crack at explaining what i've been reading, and, more ambitiously, why it might be relevant and interesting to you, i want to preface it by saying that i only have a vague idea of what i'm talking about, and i'm a little skeptical of it myself-- of the whole metaphysical project, actually. but it's more fun than i anticipated-- warmer. anyway, let me abruptly begin:

formal logic is a way of looking at the structure of arguments-- of stripping away the content to assess whether or not the thing is structurally sound. arguments transcribed or written out formally look a lot like algebra problems, but with mysterious looking symbols instead of numbers, and instead of solving for the value of variables, you assess validity. it's clear enough, i guess, why this is a useful thing to do, even if it is difficult and nerdy and seemingly removed from daily concerns-- we're not built to think so systematically on the regular, and so we are liable to be persuaded by some invalid arguments from time to time. frequently, prehaps. anyway, the point is that while we needn't all spend our lives reinventing the wheel-- justifying our systems for assessing the validity of arguments, or the nature of our methods for attaching meanings to words to objects, i do tend to hope that when and if i decide to turn my attention to the matter that it turns out our systems and methods for communicating ideas are solid enough that i can justify my sense that particular arguments and definitions can be true or false, and that there's a way of working out which it is.

modal logic is the branch of logic that deals with claims like "it is possible that..." or "it is necessary that...", or "it should be the case that...", or "he believes that...". these are truth-claims, but they're funny ones. it's pretty clear, at least in principle, how a statement like "i forgot my hat" could be assessed for truth or falsity, but what about "it's possible that i forgot my hat"? we could resolve the ambiguity by looking to see if i have the damn thing or not, but that doesn't go any distance toward proving or disproving my claim, which was that something, namely me forgetting my hat, is possible. and then there are the even tougher cases of counterfactual-- if/then claims in which the antecedent is false-- to wit: i say to my companion, "if i hadn't forgotten my hat, i wouldn't be so cold right now". she thinks (though she's too nice to say so) that if i were a little more organized, I wouldn't have forgotten my hat. now i take it that both of these claims (the spoke and the tactfully unspoken) are debatable-- maybe i think that, in fact, even if i were extremely well organized i would still, in this instance, have forgotten my hat. we seem to be disagreeing about something like which hypothetical case is more plausible or something. how in the sam hill are we suppose to establish the criterion for establishing the truth of the matter in an argument about hypotheticals?

and these sort of claims saturate our language-- everything from our most idle conversations to our most august intellectual efforts are loaded with claims about what is possible, what is probable, what is necessary. they're not about how the world is or was or will be, but how it might be or might have been, could be or could have been, must be or must have been. but how do we prove these kinds of claims true or false? they're not, in any clear way, claims about the world that we can verify.

so if you stare at them for long enough, if you relax your eyes and let them go all alien and unfamiliar-- ultra literal-- it starts to look like modal claims are not claims about the actual world at all, but claims about possible worlds. think of it this way: modal claims are claims that “there is a way things could have been” (or should have been, or might be), distinct from the way things are. note the 'is' in that claim: if we take ourselves literally, we seem to be gesturing toward the existence of something that answers the description “way things could have been”.

enter, modal realism: the theory that we really mean it when we say there is/exists a way things could have been. david lewis's theory, which is taken quite seriously by many very smart dudes is basically that all possible worlds exist. according to lewis, our world is one of an infinite number of concrete worlds, one for every possibility, and when i claim that if i hadn't forgotten my hat, i wouldn't be cold, i'm claiming that there is a possible world in which i didn't forget my hat, and in that world, i'm not cold.

stunningly bizarre: yes. but what's funny is that no one has yet come up with a clearly superior way of explaining what the fuck we're talking about when we we talk about the world as it never did and never will exist. but if you believe, even in the face of the ceaseless singularity of the world as it is, that there are many ways that it could be, it turns out that you have quite a bit of explaining to do, and you might have to make some pretty nutty claims to get the job done.


boo. said...

this post confirms a few things for me, the most important of which is that you should be watching "lost."

Lowry said...

Okay, so . . . I know I shouldn't go here, because I am not in that seminar and can't pretend to be, but I have a few questions.

If all possible worlds exist, what does "exist" mean in that sentence?

Is that statement merely tautological, or in other words, can there be an impossible world?

And if all possible worlds exist, does that help resolve the question of the truth of statements about possibilities?

laura.g said...

pei, you are such a babe- those are great questions. and since i'm on spring break AND trying to write a paper on this topic i can take a few minutes and try to answer them!

a lot of the work of the book is explaining what he means by "exist", but, roughly:

(1) they are CONCRETE, not abstract. on the one hand, this assertion that all possible worlds are concrete is what sets lewis' theory apart (there are lots of possible world theories, but mostly they argue that worlds are stories, sets of sentences, or sets of images or something). on the other hand, lewis doesn't like the concrete/abstract distinction because he doesn't think it's very clear what it is-- but goes through a whole list of things that we might mean, and says that on any account, if you insist on making the concrete/abstract distinction, the worlds he's talking about are concrete (more like tables or stars than like numbers; fully detailed; particular individuals; not abstracted from something else; having, within themselves, causal and spatiotemporal relationship).

(2) they are NOT "actual"-- only one possible world is the actual world, and that's our world. here's the catch: he wants to use the term "actual" as an indexical, like "i" or "here", just meant to specify the world that we happen to be in. so we inhabit the "actual" world, but the terms doesn't name anything "ontologically interesting"-- because all possible worlds are concrete, just as our world is. they "exist" just as ours does-- only they're not actual-- not causally or spatiotemporally related to us in any way.

impossible worlds! lewis doesn't argue for them, but he does joke about it in an illustrative way:

"the way things are, at its most inclusive, means the way this entire world is. but things might have been different, in ever so many ways. this book of mine might have been finished on schedule. or, had i not been such a commonsensical chap, i might be defending no only a plurality of possible worlds, but also a plurality of impossible worlds, whereof you speak truly by contradicting yourself...there are ever so many ways that a world might be; and one of these many ways is the way that this world is."

and as for your third question, it's a doozy. a lot of people say no for a whole bunch of different reasons. the one i'm writing about right now (and the one i'm most interested in) is that lewis does indeed establish truth conditions for possibility statements (it is possible if and only if it is true at some world), but we can never verify whether it IS true, because we can't investigate other possible worlds. i'm tempted to argree emphatically with this objection, but this might be based on some unfair assumptions about what lewis thinks of as his project. i'm going to be a little vague here, because i can't quite figure it out yet, but one response to the criticism might go something like this: when we talk about what's possible we're very often discussing worlds that MIGHT BE OUR WORLD (for all that we know). the information that we're really after we can find by investigating our own world, trying to figure out what world it IS. and anyway if possible worlds were the sorts of things that we could investigate, they wouldn't be the right sorts of things to a underwrite our modal talk.

so now i've ended by talking about the role of our epistemic limitations in motivating our claims about possibility-- which is what one of your other comments is about, if i remember correctly.