140 Paul Sheldon Davies
contrary to Ruse, we ought to resist the urge to conceptualize the parts of plants and
animals “as if” created by an intelligent mind. That, after all, is the lesson learned from
the directives in (D) and (P). The lesson learned from (D) is that the long historical roots
to which Ruse appeals in support of his metaphor should instead lead us to reject any such
metaphor. We should withhold antecedent authority to our concept “purpose” precisely
because it descends to us from a worldview (or a set of worldviews) we no longer regard
as true or promising. The lesson learned from (P) is that the felt intuitive force of our
concept “purpose” is no grounds for trying to preserve the concept. To the contrary, we
should withhold antecedent authority precisely because we have discovered that the
concept has undue force in our psychology. Instead of continuing, therefore, to conceptual-
ize the parts of plants and animals in terms of normative functions, we should, in light of
what we know about our intellectual history and our cognitive capacities, withhold ante-
cedent authority to this concept. We should also try to extend our current concepts or create
new ones, in an effort to think or feel differently about living things, that we might con-
tribute to progress in knowledge.
The basic point against Ruse is in fact on the surface of his own discussion. Darwin
killed literal design in the realm of the living; that, according to Ruse, is something we
know to be true. We have therefore the cognitive capacity to see that living things are
devoid of purposes. At the same time, we know from the study of our own psychology
that we are inclined to see purposes among the parts of plants and animals even though
none exists. We have therefore the cognitive inclination to see part of the world falsely
with regard to “purpose.” And all this is to say that one part of our psychology enables us
to see that another part tends to lead us astray. Why, then, surrender to the part that we
know is leading us away from the truth? To do so is to engage in a particularly destructive
form of conceptual conservatism. It is surely not among the methods likely to contribute
to the growth of human knowledge.
And there is a further point against Ruse’s metaphor. It is simply not true, despite his
assertions to the contrary, that evolutionary theorizing would grind to a halt were we to
forego the attribution of normative functions. We have, after all, an alternative theory of
functions that eschews the imputation of functional norms, namely the theory of systemic
functions. As I argue elsewhere, we can conceptualize functions as nothing more than the
effects of systemic components that contribute to some higher-level systemic capacity, and
we can, at the same time, justify all the function attributions we wish to make in the course
of theorizing about the evolutionary history of life on earth. The only thing we lose is the
imputation of the alleged norms of performance, that is, the property of “being supposed
to” perform a given functional task.^15
We have, then, two basic parameters with which to frame our inquiry. We have an
alternative theory of functions—the theory of systemic functions—and we have the direc-
tives for inquiry described earlier—directives based upon the historical and psychological
dubiousness of the concept “purpose.” It is, in light of these parameters, naïve to insist