FUNCTIONS
Tim Lewens
1 THE PROBLEM OF BIOLOGICAL FUNCTIONSThe problem of biological functions arises because biologists’ use of the function
concept appears distinctive in comparison with that of physicists or chemists.
True enough, physicists and chemists ask questions about functions. A chemist,
for example, might try to ascertain the precise function of some reagent in an
inorganic process. But in articulating the function of chlorofluorocarbons (CFCs)
in the breakdown of atmospheric ozone the chemist would not suggest that CFCs
are for breaking down ozone, nor that she has discovered the purpose of CFCs, nor
would she think that she has somehow explained why CFCs feature in this system
of reactions. Compare this with a claim like ‘the function of the peacock’s gaudy
tail is to attract mates’. Here there is, on the face of things at least, a strong
connotation that peacocks’ tails are for attracting mates, that the purpose of the
peacock’s tail is to attract mates, and that attracting mates somehow explains why
peacocks have such gaudy tails. Let us call function talk that carries some or all of
these connotationsheavy function talk, and function talk of the more modest form
that our chemist useslight function talk. In day-to-day life it is in the contexts of
artefacts designed by intelligent agents, or actions performed by intelligent agents,
that we tend to find this kind of heavy function talk. Hence one might harbour
an initial suspicion regarding the propriety of heavy function talk in biology.
Very broadly speaking, there are four types of reaction one might have to these
preliminary observations, and to the suspicions they give rise to. The first is to
argue that serious biologists do not make use of heavy function talk at all; perhaps
this appears in some popularisations of their work, but it is an exaggeration to
think that it plays any role in the practice of the science. The second is to concede
that while some biologists do use heavy function talk, these biologists are making
a simple mistake, for talk of this kind has no business in a grown up science. The
third is to argue that heavy function talk is justified, and even useful, but not
because it is true of organic systems: rather, function talk is metaphorical, or its
use relies on analogies of some kind between organic systems and other systems
(most obviously artefacts or actions) where heavy function claims can be asserted
truly. The fourth option is to argue that heavy function talk is justified in biology,
and to argue that it can be truly asserted of biological systems, in virtue of their
instantiating purely biological properties.
General editors: Dov M. Gabbay,
c
Handbook of the Philosophy of Science. Philosophy of Biology
Volume editors:
Paul Thagard and John WoodsMohan Matthen and Christopher Stephens
©2007 Published by Elsevier B.V.