526 Tim Lewens
Recent philosophical work on functions has come down overwhelmingly in favour
of option four ([Matthen, 1997], who favours option three, is an exception). That
is surprising, because every one of these options offers some promise of achieving
what is probably the major goal of modern philosophical analyses of function,
namely, to come to an understanding of the appearance of function talk in biology
without the need to invoke either reverse causation or divine design [Buller, 1999a,
19]. One of my main aims in this essay is to encourage further exploration of the
other three options.
2 ORGANISMS, ARTEFACTS, AND AGENTSThe four options I outlined in the previous section concerned what kind of signif-
icance we should attach to function talk in biology. There is another important
distinction, orthogonal to this one, that concerns how we are to analyse that talk.
This distinction is between theories of biological function that take their inspira-
tion from what I call theartefact modelof organic function [Lewens, 2004], and
theories that take their inspiration from theagent modelof organic function. In
the first case, one sees the functions of organic parts as similar in kind to the
functions of the parts of artefacts. In the second case, one sees the organism as a
whole as akin to an agent aiming at some goal.
Agents have goals in virtue of facts that are internal to them: what an individual
is aiming at is a matter of his motivational states, his dispositions regarding what
kinds of events would cause him to cease his search, or some such. (I am ignoring
complications presented by externalist accounts of mental content.) Accounts of
function that draw on the agent model explain the presence of heavy function
talk in biology by seeking facts about the internal organisation or development
of organisms, which are analogous to those facts about an agent’s motivations
that make it the case that the agent has a particular state of affairs as its goal.
Agent-based accounts of function talk in biology consequently tend to regardgoal-
directednessas the basic notion to be analysed.Functionsare logically secondary
to goals: functions of organic parts or processes are contributions to overall organic
goals.
Artefact-based accounts tend to reverse the logical relationship between the
functions of the parts and processes of organisms and organisms’ goals. (This
says nothing one way or the other about whether they make functions more basic
than goals in general.) Artefacts have their functions in virtue of facts external
to them: what a tool is for depends on its history of design or its pattern of use,
not on its internal organisation. Accounts of function that draw on the artefact
model explain the presence of heavy function talk in biology by seeking a biological
process that is external to organisms themselves, and which is analogous to the
processes of design or use that ground function claims in the context of artefacts.
Accounts of this sort are often illustrated using organic traits which are more nat-
urally described as functional, rather than goal-directed. Although the eyespots
on a peacock’s tail may have the function of attracting mates, it seems strained to