Compositional Vagueness in Material Objects

I recently attended a conference in Nottingham entitled 'New Directions in Metaphysics', hosted by the University of Nottingham. The venerable Dean Zimmerman was there, giving a talk on property dualism. His talk didn't excite me too much, but when he brought up the well-known problem of the vagueness of composition, it got me thinking again on these questions.

To refresh your memory, the problem of the vagueness of composition arises if we consider a reasonable definition of a material object - say, a human being. Suppose that a human being is defined as being that object that is composed of all of these material elements - say elements a1-an. This seems fairly straightforward, until we consider that it is very hard to, as it were, draw a line around those elements that compose us and those that do not. In fact, when we get a very detailed, close-up view of these elements, it becomes more and more obvious that there are many different elements that are just as entitled to be a part of an object as the ones that we at first chose to countenance. That is, there are many different sets of elements that are up to the task. Or consider another analogous problem: take all of the elements that one might say composes a particular human being (a1-an) and ask yourself whether or not it would be acceptable to define this human being by excluding merely one of these elements - say a3. Repeat and repeat the thought experiment until you reach absurdity.

This seems like a fairly important problem for defining material objects - for once the thought experiment is carried out, there seems to be an extremely large group of acceptable candidates, none of which seem to have any special claim to being the set that defines a particular material object.

An interesting response to this problem is the one given by Peter vanInwagen, who claims that the only material objects that exist are those that are biological - and they are individuated by being a particular group of elements all participating in the biological functioning of an object. Any of those fringe elements that made-up other candidates won't be acceptable then, as they are not aiding in the biological functioning of the object in question - they are, as it were, just idly floating about. Of course, a well known problem for this kind of view is that it entails that things like 'tables' and 'chairs' don't exist. It's a bullet that not many have particularly wanted to bite.

For my part, I think vanInwagen's response is on the right track in a certain respect, in that it individuates material objects using a certain dynamic criterion. It seems to me that the reason that the 'many candidate' problems all get started by assuming that the individuation of a material object must be a merely static - in the case of Lewisian examples, a particular set of elements. There is, of course, something to be said for wishing one's identity criterion remain stable - for instance, you don't want it to be the case that the identity criterion for a material object is constantly changing full stop. But the set-theoretic element identifications are inadequate, I think, because they fail to have any dynamic qualities at all.

I suppose the reason for this is mostly historical . Couple the fact that analytic philosophical methods have always wanted identity to be a stable, unchanging primitive fact with the further fact that the concepts of mathematics have always been considered the most unchanging facts and there's good reason to follow this kind of idea through. But it's hard for me to take any of this seriously in light of the current state of metaphysics, physics and the developments in quantum mechanics. As far as I can tell, all the evidence in quantum mechanical physics points towards defining physical objects as dynamical - the wavefunction is certainly, if anything at all, a dynamic representation of reality. If the wavefunction does represent something physical, it represents something that is not merely 'categorical', and certainly doesn't represent it as simply a set of particular elements; think here only of the fact of wave-particle duality! And metaphysics too, riding the crest of scientific discovery, is edging more and more towards an ontology of dispositions and propensities. So why should we be persuaded by thought experiments involving 'candidates' that are unchanging, static sets of elements?

There's every reason to believe that a better criterion of material object individuation can be given by something that is unchanging and yet has a dynamical aspect - perhaps dispositionally, via (Lorentz) invariant mass; cf. Leibniz, who once defined substance as 'a principle of action and passion'. Under this general criterion, we may define a material object by picking out its fundamental dispositional properties. This kind of analysis certainly has no concern for which elements 'belong' to to an object and which do not and makes the rival candidates of Lewis' thought experiments seem much less interesting.

It might still worry one that this kind of individuating technique leaves open the question of which elements of a set truly belong to a material object and which do not. But I'm not so sure that this is much of anything to truly be worried about. If a material object is defined by (and perhaps, is essentially) a set of fundamental dispositions, asking which material elements belong to it and which do not is not asking anything very interesting about it - unless, of course, one thinks that the contingencies of the moment-to-moment career of the object in question is of any real importance; it certainly isn't important for scientific inquiry at any rate.