Darwinian Naturalism, Theism, and Biological Design

Timothy Shanahan

A curious tension seems to exist at the center of Darwinian Naturalism. On the one hand, Darwinian Naturalists are fond of stressing the power of natural selection to produce the extreme adaptedness and the virtual perfection of the structural and functional properties of living things. Unlike their natural theologian forbears, however, they wish to insist that such perfection comes about without assistance from any sort of divine Mind orchestrating this process. One need only recall the last nature documentary watched featuring animals displaying protective camouflage -- stick insects indistinguishable from the twigs they rest upon, caterpillars that resemble bird droppings, and the like -- to see the full force of the Darwinian Naturalist claim that the entirely opportunistic process of natural selection has the power to shape organisms to an almost unimaginable degree of perfection.

On the other hand, one of the commonest and most persuasive arguments used by Darwinian Naturalists against the hypothesis of special creation or divine control of the evolutionary process starts from recognition of the all-too-common instances of imperfection to be found in the living world -- e.g., halibut (flatfish) which lie on the seafloor with one eye grotesquely rotated around, deforming the skull, retinal tissue oriented "backwards" in the human eye, and the like. Instances of such biological "contraptions" suggest a more haphazard evolution of organic structures unbecoming the craftsmanship of a divine Designer. Surely, the Naturalist argument goes, even the most vulgar human craftsman could be expected to avoid such gross incompetence; should we expect anything less from an omnipotent Designer? Consequently, Darwinian Naturalists seem to be committed to acknowledging both the extreme perfection of some organisms (or organic structures) along with the obvious imperfection of others.

Is this a consistent position? Are Darwinian Naturalists trying to have it both ways by selectively emphasizing those features of living things that best suit their rhetorical purposes at the moment? Is this a weakness of Darwinian Naturalism that can and should be exploited by Theists? I propose to answer these and related questions by examining the notion of "biological perfection" implicit in discussions of the "design" of living things. I begin with a brief overview of pre-Darwinian views on the degree of perfection to be found in the design of living things, describe Darwin's own shifting position on this issue, and finally consider some contemporary debates on the status of "adaptationism". I will argue that while the inconsistency in Darwinian Naturalism is only apparent, this does not give the victory to Naturalists. Instead, a fuller understanding of this issue throws into greater relief the deeper philosophical issues dividing Naturalists and Theists.

Copyright © Timothy Shanahan