Friday, November 4, 2011


I'm not sure I believe in metaphysics.  Perhaps I do. Do my speculations about the minimal requirements for a world in which a mind could evolve constitute metaphysics (“A World for Mind” Sept 2009)?  They may mix in too much practical observation to satisfy some philosophers.  But in any case, some classical efforts at metaphysics, in the sense of using pure reason, free of any empirical evidence, to determine necessary truths about the world, seem to turn on a confusion of observations about human cognitive processes with observations about the underlying reality.

I am thinking of Saul Kripke's Naming and Necessity (which I’ve just read) when I write this.  (I realize there’s some hubris in someone like me critiquing a philosopher of the status of Kripke, but hey, that’s what Persistent Wondering is all about...)  Kripke’s ideas on naming and reference make a lot of sense to me.  I don’t find anything to object to in the idea that names, both of particulars and of general terms, are used to fix a reference, and not, at least in most cases, as a shorthand for a definition.  But when he extends this idea, through possible worlds and the idea of a name as a rigid designator, to questions of identity and necessity, he leads where I find myself unable to follow.

Kripke’s first references, in the book, to the idea of possible worlds strike me as very insightful and important.  He says that “possible worlds are stipulated, not discovered by powerful telescopes.”  Thus, to use his example, if we stipulate, in our counterfactual situation (possible world), that Nixon lost the election, we also stipulate that we are talking about Nixon, and we do not need to go to great lengths to prove the “identity” of the two Nixons in our actual and counterfactual worlds.

I think possible worlds are stipulated.  I think further, they are stipulated for some purpose, perhaps rhetorical, perhaps analytical, in the sense of trying to derive general rules about the universe from observations of particulars (in the rest of this essay, I will try to use “model” and “modeling” in place of “analysis” in this sense to avoid any possible confusion with the notion of “analyticity” as used by e.g. Kant or Kripke).  We stipulate those aspects of deviation from our world as are deemed necessary for our purpose.  The default assumption is that things not so stipulated, and not derivable from things so stipulated, are “the same as” in our world, but in fact, if these things are essential to our model, then this sameness also must be stipulated.  So really, aspects of the possible world which are not in some way stipulated are simply unknown – and we don’t care, because they’re not relevant to our model.

The process of reasoning about a possible world is almost exactly like the process we use to try to predict the outcomes of sequences of events in the real world, and I am certain we use the same cognitive faculties to do both tasks.  There is a difference in intention, though.  When we say “What would A have done if B?” our interest is presumably only academic.  But when we say, “What would A do if C?” we may have a direct interest in the answer.  For example, it may help us decide whether or not to act so as to try to bring about condition C.

But, in any case, a possible world is just a mental construct.  It is a modeling tool.  It is not “real”, in the sense that our world is real.   Of course, it is real, in the sense that our thoughts are real, but questions like the “identity” of objects between possible worlds tell us only about how we think or speak.  They do not tell us anything directly about reality.  They are issues of semantics, or epistemology, not, as near as I can tell, about metaphysics.  Modeling via possible worlds tells us something about the world only if  (1) we are using the model explicitly to explore the relationships between things in the real world, (2) we have all the relevant data, and (3) we reason correctly.

Consider some of Kripke’s examples.  He argues that in our world the astronomical entities Hesperus, Phosphorus and the planet Venus are, in fact, one-and-the-same object; therefore Hesperus=Phosphorus is a necessary truth, although, in a sense, contingent.  It is contingent, because we “could have” discovered that the two names represent distinct objects.  But they do not.  When we speak of a possible world, we do so in our own language, not in the language stipulated for the possible world.  In our language “Hesperus” and “Phosphorus” are names for the same object.  If we stipulate a possible world in which “Hesperus” and “Phosphorus” are used to name two different objects, we would say that one, or both of them, is not Hesperus=Phosphorus.  Thus Hesperus=Phosphorus is true, and true in all possible worlds (even those in which the terms are used – in the language of that world – to reference different objects), hence necessarily true.  I don’t really do justice to Kripke’s argument.

Now, if I were reasoning about a possible world in which “Hesperus” or “Phosphorus” referenced different objects, I don’t know if I would say “consider a world in which ‘Hesperus’ and ‘Phosphorus’ referenced different objects,” or “consider a world in which Hesperus and Phosphorus were not the same,” but in any case, my manner of speaking certainly doesn’t tell me anything directly about whether Hesperus and Phosphorus really ARE the same.  It seems to me like Kripke is just saying “imagining things to be different doesn’t make them different,” with which I agree.  But a notion of  “necessity”, so defined, doesn’t seem very useful.  Maybe he’s saying something more, about objects and names, something like, “if two (or more names) are used to reference the same object, the object referenced by any of the names is always the same object” – i.e., something is always identical to itself.  This seems at first blush to be trivially true, but I guess I’ve seen some such notion appear in some axiom system often enough that I can accept that maybe it’s not, at least quite.

Kripke’s cats/demons argument (which he attributes, in it’s original form to Hillary Putnam) is another interesting example.  Kripke argues that it could have turned out that cats were not animals, but demons, who chose to look like cats, and to exhibit all the behaviors we associate with cats.  But it did not turn out that way – cats are animals, not demons.  So being an animal is a necessary, or essential, property of cats.  If we stipulated a possible world in which all cats were actually demons, we would say that in that world there were no cats, only demons acting like cats.  Well, I don’t know.  I just stipulated the possible world by saying “all cats [are] demons.”  But, in any case, how we stipulate a possible world doesn’t tell us about anything except how we talk, or, at best, how we think.  So Kripke’s definition of “necessity” as “true in all possible worlds” again seems rather meaningless.  Kripke’s example seems to reduce to “given that cats are not demons, cats are not demons,” which this time really seems to be trivially true.

Kripke’s line of argument becomes more pernicious (potentially, although he refrains from carrying it to a dualist extreme) when he speaks of mental and physical states.  Kripke essentially argues that a mental state cannot be identical with some corresponding physical state, because we can conceive of them separately, and separable.  He contrasts this with heat and molecular motion, which he holds to be identical, because, when we imaging heat separable from molecular motion, what we are really imagining is the sensation of heat, not heat, itself (which is molecular motion), but the sensation of pain, for example, is simply pain, so when we imagine pain separable from the stimulation of nerve fibers, we are really imagining two different things.  Again, I don’t do justice to his argument, I’m sure.

Maybe Kripke and I have different meanings when we talk about “things” being the same or different.  If Kripke means the concept of pain is distinguishable from the concept of a physical state, then I would agree.  These concepts are certainly things or objects (mental objects).  But if we believe these concepts refer to something in the “real” world, then the fact that the concepts are distinct does not prove that the things referenced are.   (I apologize for the scare quotes on “real”.  Language fails me, here.  “Non-mental” world?  Is pain non-mental?)  I do not believe it is actually possible for pain to exist without the corresponding physical state, any more than I believe it is possible for heat to exist without molecules in a state of agitation.  Nor do I believe that it is actually possible for  the physical state corresponding to pain to exist without there being pain (more on this in a moment).  Whether such an state of perfect one-to-one correspondence as I describe should be termed “identity” is a linguistic question.  It has nothing to do with physical reality.  Even if I am wrong, the mere fact that our concepts are separable is information on how we think and speak, but tells us nothing about the world.  It is an epistemological and semantic datum, not a metaphysical one.  Unless metaphysics means something entirely different than I would think.  (Hence my opening doubt, which questions whether metaphysics really means anything not contained in semantics and epistemology.)

I should note that Kripke’s (circa 1972) notion of “physical state” seems to me probably inadequate, which may partially explain his resistance to equating physical and mental states.  I’m reading between the lines, here, but I think he conceives of such physical states much too locally, on the order of stimulation of a few nerve fibers.  I think the equation of mental and physical states requires a much more wholistic notion of physical state.  Thus a dead man, or an anaesthetized one might have certain fibers stimulated, and not feel pain – the rest of his physical state is not arranged conducively.   I also sometimes think there may be a useful (i.e., meaningful) distinction between feeling pain and being consciously aware of feeling pain (may apply, for example, to a person in a coma), but I’m not really sure this distinction turns out to have explanatory value.

All of this makes me want to go back and reread some of Quine’s critiques of the concepts of necessity and analyticity, to see if I now get more out of them, now.  I freely admit that as an amateur philosopher, I’m a pretty good structural engineer.  I may be missing more than a few subtleties.  Still, I can’t keep from wondering...

1 comment:

  1. Very nice and interesting post. I think that one way to think about possible worlds is to think about modal logic. I remember that my philosophy teachers at school tended to think that modal logic was bunk, and therefore dismissed "possible world" reasoning altogether. The fact that so much needs to be stipulated to use your language made them suspicious. However, to logically justify mathematics, it seems that you need to stipulate all kinds of things. Look at Russell's problems and the problems with set theory. Is modal logic more dubious than mathematics? Anyway, thanks for the post and sorry it took me so long to comment.