Conceptual Conservatism 139
8.3 Normative Functions
Armed with the directives for inquiry just described, I return to my opening question: Why
are we concerned to theorize about the apparent purposiveness of living things? Here are
two possible answers:
- We are concerned to develop a theory of natural purposes because natural purposes
in fact exist; we want to understand the origin and nature of a real feature of the natural
world. - Natural purposes do not exist but we nevertheless are concerned to develop a theory
of natural purposes because we are psychologically constituted in such a way that we
cannot help but conceptualize the parts of plants and animals at least metaphorically in
the same way we conceptualize artifacts.
The fi rst answer asserts that there is nothing puzzling about our concern to theorize about
normative functions since such norms are clearly part of the natural world. The second
answer says that it is a mistake to attribute such norms to the natural world, but that,
because of the structure of our psychology, the attribution of these norms is indispensable
to the very existence of evolutionary theory. Both answers have been defended in the
recent literature. Yet neither is defensible from the perspective provided by my directives
for inquiry. The only way to defend these answers is to fi rst defend something indefensible,
namely, the commitment to conceptual conservatism.
Begin with the second answer. Michael Ruse has recently argued that although Darwin
effectively destroyed our belief in any literal design in the living realm, we nevertheless
cannot do without the metaphor of design. This is a thesis concerning human psychology.
We are condemned to seeing the parts of plants and animals “as if ” created by an intelligent
mind for some specifi c purpose. And it is a good thing, according to Ruse, that we cannot
help but see the living as purposive, since evolutionary biology would otherwise be impos-
sible for us. We would lose the capacity, he claims, to ask “why” and “what for” questions.
We would be helpless to initiate the search for adaptationist explanations: “Without the
metaphor, the science [of evolutionary biology, at minimum] would grind to a halt, if
indeed it even got started” (Ruse 2003, 285). Ruse defends this thesis in part by appealing
to a handful of case studies, including the double lens of the trilobite, but mostly by
appealing to the long historical roots of the concept “purpose.” Indeed the bulk of his
discussion traces the genealogy of this concept from Plato and Aristotle through Kant,
Paley, and Darwin. And Ruse is clear that the stubborn persistence of the concept, evi-
denced by its long historical roots, is supposed to lead us to the conclusion that “purpose”
is indeed a concept we cannot do without.
If, however, my directives for inquiry are plausible, then we cannot endorse Ruse’s
metaphor. We should agree with Ruse on two points, namely, that we humans are inclined
to see living things as purposive and that living things are not, in fact, purposive. But also,