A few months ago, I began reading a book by the sociologist Christian Smith called What Is a Person?--concerning which, though it is very interesting, I have nothing of consequence to report just at the moment. I mention it here only because its early chapters reminded me of a topic upon which I have intended to write for some time. Among the most crucial supports for Smith's central argument, you see, is an extremely strong concept of natural "emergence": that is, the seemingly simple idea that in nature there are composite realities whose peculiar properties and capacities emerge from the interaction of their elements, even though those properties and capacities do not reside as such in those elements themselves.
An emergent whole, in other words, is more than--or at any rate different from--the sum of its parts; it is not simply the consequence of an accumulation of discrete powers added together extrinsically, but the effect of a specific ordering of relations among those powers that produces something entirely new within nature.
This proposition is, of course, quite true in a general sense; but it is also quite false in several specific senses, and most especially in the sense that Smith gives it. According to him, an emergent reality is one that, though remaining ever dependent upon the native properties of the elements composing it, nevertheless possesses new characteristics that are wholly "irreducible" to those properties.
But this is certainly false. At least, as a claim made solely about physical processes, organisms, and structures--in purely material terms--it cannot possibly be true. If nothing else, it is a claim strictly precluded by most modern scientific prejudice. From a genuinely "physicalist" perspective, there are no such things as emergent properties in this sense, discontinuous from the properties of the prior causes from which they arise; anything, in principle, must be reducible, by a series of "geometrical" steps, to the physical attributes of its ingredients.
Those who think otherwise are, in most cases, merely confusing irreducibility with identity. Smith, for instance, uses the example of water, which, though composed of the two very combustible elements hydrogen and oxygen, possesses the novel property of extinguishing fire; therefore, says Smith, water "is irreducible to that of which it is composed." But it is nothing of the sort. Yes, water's resistance to combustion is not identical...