Functions 527say that attracting mates is their goal: after all, the eyespots are not responsive
to the presence of mates — their structures are static. To the extent that parts
of organisms, or organic systems, are regarded as having goals this also rests ulti-
mately, for artefact-based theories, on biological processes external to organisms.
According to these views, just as a thermostat has the goal of regulating heat in
virtue of its design history, so homeostatic systems aim at maintaining organic
equilibrium in virtue of their histories.
The artefact/agent distinction is not intended to be exclusive. One could, for
example, fashion a theory of functions around the conception of organisms as
agents whose traits are their tools. Another conception, encouraged by the widely-
used distinction between replicators and vehicles, is of genes as agents, and of
organisms as the tools used by genes to enable their replication. One might wonder
whether all theorists of biological function who adopt some variant of the ‘artefact
model’ for the functions of organisms and their parts must eventually find some
biological analogue to an agent. After all it is plausible to think that in the domain
of artefacts, the external facts which fix the functions of tools ultimately depend on
intentions, which in turn depend on the goals of agents. This may explain, in part,
why Daniel Dennett [1995] sometimes casts the role of the evolutionary biologist
as that of ‘reading Mother Nature’s mind’: he conceives of natural selection in
the abstract as an agent, and of organic traits as tools designed by that agent.
The job of the biologist, says Dennett, is to discover (metaphorically speaking)
what Mother Nature had in mind in building organisms one way rather than
another. I do not propose any solution to the question of whether goals are always
conceptually prior to functions here. The role for the artefact/agent distinction
is merely to explain some of the initial directions in which philosophical analyses
of the function concept proceed. To recap, some theorists look to organisms’
developmental and regulatory processes to justify a view of the organism as akin
to a goal-directed agent, while others look to evolutionary processes to justify a
view of the organism as akin to a collection of designed tools.
The artefact/agent distinction is orthogonal to the fourfold distinction I in-
troduced near the beginning of this essay because, to take just one example, re-
gardless of whether we think function talk in biology is literally true of biological
systems, or merely expresses a series of fruitful metaphors, we would still have
to decide whether that talk should be analysed and explained in ways that relate
organisms to goal-directed systems, or to designed systems, or to both. Almost
all contributors to the debate over the past twenty years or so have adopted an
artefact-based model of function. Once again, a central aim in this essay is to ex-
plore the prospects for agent-based models, and to encourage others to give these
accounts a second chance.
There is a long tradition in British biology in particular that focuses on the
similarities between organisms and artefacts, and it is surely this tradition that
explains why artefact-based accounts of function are so prevalent in philosophy of
biology today. This tradition can be observed most clearly in the work of Natural
Theologians like William Paley [Paley, 1802]: for these writers organisms were