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Book Review - Norms of Nature
Norms of Nature
by Paul Sheldon Davies
MIT Press, 2001
Review by Ed Brandon
Oct 18th 2001

While it may be, as Fodor has said, that "it wasn't God that Darwin killed, it was Mother Nature," there continues to be a need to ensure that we don't fall back into outmoded and mythological ways of thinking. Davies' book is a sustained attack on what he sees as one such rearguard action, ironically one that places Darwin's own theory of natural selection at its core.

Biological thought has always revolved around the notion of function. Recent philosophizing about biology has often attempted to show how this notion can be regarded as naturalistically legitimate, how its apparent appeal to purposes or the intentions of some sort of designer can be explained away. Since the work of Cummins and Wright in the mid-1970s, it has been common to contrast two general approaches to the analysis of function in biology, associated with these two authors. A Cummins view (a systemic account) emphasizes the idea that for something to have a function is for it to make a contribution to a wider system - so, to take a standard example, the fact that one function of the heart is to pump blood is seen as telling us that the heart's pumping blood is its contribution to a wider system for the distribution of nutrients around the body. A Wright view (a selective account) on the other hand emphasizes the history that has led to us having hearts: ancestors with hearts that pumped blood well dominated those that lacked hearts altogether or whose hearts did not pump so efficiently, so today we have hearts that pump blood.

It appears that one problem with systemic accounts is their "promiscuity" - hearts do lots of other things in other systems (e.g. make noises that doctors use for diagnosis) but we are not inclined to think of these as functions of the heart. And here a selective account has an obvious answer: hearts were selected because of their role in pumping blood but were not selected for their capacities to make noise. Selective accounts also appear to be able to ground our idea that organs can malfunction, that there are norms of performance in the nature of things: hearts are the outcome of a selective history focused on pumping blood, so pumping blood is what they are supposed to do, so we can objectively judge that something has gone wrong when a heart is unable to pump blood.

Davies sets out to show that these appearances are false. One line of argument is that functions understood systemically are unavoidable. Before a biologist starts telling a story about selective history (and Davies reminds us that getting evidence to support such stories is far from straightforward), he or she must have identified something that at least has a Cummins-style systemic function here and now. Although it is possible that every specimen of a species should begin to malfunction, if we imagine coming upon a totally alien life-form for the first time we would not in such a case have any ground for identifying the proper function. (In not so alien cases, structural similarities might well guide our thinking - a cave-dwelling species of animal has things that are in the right place to have been eyes.) Davies further argues that the typical explanatory focus of selective function accounts - the persistence of a feature in a population - can be handled systemically by treating the population itself as the relevant system and taking selection as a causal process within such a system, so the systemicist can give us all the historical explanations promised by the selective account.

To counter the promiscuity objection, Davies claims that to invoke a function is to think in terms of a hierarchical system: a function is a contribution to a higher-level capacity of a system. He seeks to show that some of what critics have claimed must be taken as systemic functions are not functions at all because we do not have the right kind of hierarchical system - the water cycle is a mere cycle, like the seasons, not a hierarchical system like the menstrual cycle, so we need not think that clouds have a function of producing rain to encourage vegetative growth; the solar system lacks the right sort of hierarchy, so we need not think that one of Uranus' functions is to perturb the orbit of Neptune. While this move may allow Davies to make a distinction in some cases between functions and mere effects, he has to allow that there are a lot of functions to be found since so much of the world is hierarchically organized. So he is prepared to be somewhat more promiscuous with respect to function-attributions than the man in the street, or at least in this philosopher's armchair.

The negative lines of argument point to weaknesses in the selective history account - which history is relevant? does it have to be a matter of natural selection? In general it seems that our judgment about whether we have a function determines the answers here, whereas it ought to be the other way round on a selective account - and in particular to the rejection of its central idea of natural norms. For this Davies has two main strategies. One is to ask what possible naturalistic sense we can give to the idea that something is "supposed" to do something, when the only facts are that ancestral counterparts were selected because they did it. We may create expectations, but a history of selection cannot. Davies offers a Humean story in which our epistemic expectations (most of the hearts we have examined have pumped blood and we have begun to see the systemic structure involved, so we expect this one to as well) are the basic cause of our regression to pre-Darwinian notions. While it may be odd to think of Millikan, Dretske or Kitcher as hankering after non-anthropocentric norms, Davies has at least offered them the challenge to spell out what kind of normativity a history of differential reproductive success is meant to create, and when Plantinga has argued that proper functioning can only be understood within a supernatural context we are surely due an account that unambiguously dispenses with such excesses.

The second line of attack is intended to show that the supporters of selective accounts cannot in fact deliver on their claimed derivation of the intelligibility of malfunctions. If natural selection is going to operate on some entity, we need three categories: a generic type containing variations, a narrow type not selected for, and a narrow type selected for. (The narrow types will no doubt contain some variation, but not as much as the generic type.) Taking the heart again, Davies asks us what is to count as a heart in a selective account of heart function. Present-day hearts have been selected for pumping, so they are tokens of the third category, a category defined in terms of its success in pumping. But when an object that cannot pump is said to be malfunctioning it is being identified, not as a token of the third category, but as one of the first, generic category. And the story that supposedly gives rise to a natural norm doesn't apply to things in that category. (On Davies' own showing, such an incapacitated object may well belong to the second narrow category. What would that tell us to do? I think this shows how any norm we might associate with it derives, not from the nature or history of things, but from our own interests.)

Davies has many detailed discussions of issues relating to function in the philosophy of biology and of what the invocation of function by biologists actually achieves, and he well shows the resources available if one wishes to eschew any appeal to history in one's analysis of function-attributions. It is perhaps unfortunate that he has focused so narrowly on issues in biology - in a couple of places he explicitly and perhaps too hurriedly rejects attempts to unify biological functions with intentional design, but he nowhere refers to discussions of the interpretation and legitimacy of functions in sociological theorizing, for instance, which may point to a greater role for some type of historical appeal than he is prepared to concede.

© 2001 Ed Brandon

Ed Brandon is, by training, a philosopher, and now is working in a policy position in the University of the West Indies at its Cave Hill Campus in Barbados.