16 March 2008

Naturalism and Evolutionary Theory

I recently sendtwell-known professor Alvin Plantinga an email about an article he wrote on the relationship between religion and science. Contra most scientists, as well as philosophers of science, Plantinga argues not just that the two are compatible, but that science actually supports religion (specifically Christianity).

In his email response, Plantinga (correctly) states that evolutionary theory does not entail naturalism: one can be both a theist and an evolutionist without logical-theoretical contradiction. Indeed, one can choose to believe that God (or aliens, or an invisible pink elephant) guides each “random” genetic mutation, resulting in anagenesis and eventually extinction or speciation. No problem here.

But, as I state in my email reply, the important point is that evolutionary theory explains the phenomenon of transmutation (i.e., species change) over time just fine without reference to supernatural agency. In this sense evolutionary theory is naturalistic. Any postulation of supernatural guidance of mutagenesis—or selection through environmental changes or predation, and so on—is to multiply entities beyond necessity, upsetting the loyal Ockhamist.

To be clear, Darwin’s great contribution was not the idea of evolutionary change over geological time. Indeed, numerous biologists before Darwin had proposed similar ideas, dating all the way back to the pre-Socratic philosopher Anaximander and including Darwin’s own grandfather, Erasmus Darwin, who authored Zoonomia.

Rather, in contrast to the Lamarckian mechanism of inheritance of acquired traits (which Darwin nevertheless accepted as a subsidiary mechanism of evolution), Darwin proposed the mechanism of natural selection. According to Darwin’s “selectionism,” populations exhibit variation of characters, some of which are more advantageous than others. Thus, because of the (Malthusian) struggle for survival, the organisms in the population have varying abilities to survive, which leads to differential reproduction. Consequently, the organisms well-adapted to their environments will survive, while the others die off.

The Darwinian mechanism, as the term itself suggests, is mechanical. Thus, in response to Plantinga’s objection, one needs to posit supernatural guidance of random mutations no more than one needs to posit such guidance for moving a boulder with a lever. Both occur purely mechanically. And the laws of nature account for the lever—as well as natural selection—perfectly well. Thus, positing that God guides random mutations is unnecessary and absurd.

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