Darwin’s Doubt: Naturalism’s Epistemology Problem

In a letter dated July 4, 1881 Charles Darwin wrote William Graham congratulating Graham on his book Creed of Science. Darwin wrote, “Nevertheless you have expressed my inward conviction, though far more vividly and clearly than I could have done, that the Universe is not the result of chance. But then with me the horrid doubt always arises whether the convictions of man's mind, which has been developed from the mind of the lower animals, are of any value or at all trustworthy. Would any one trust in the convictions of a monkey's mind, if there are any convictions in such a mind?”  What did Darwin doubt exactly, and what bearing do his reservations have on contemporary neo-Darwinian theories of evolution?

While Darwin’s words are subject to various interpretations, many philosophers have argued that Darwin doubted whether the human brain, which he understood to be the product of a blind evolutionary process, could be trusted to supply human beings with accurate information of the world around them. There is, after all, no guarantee that natural selection will ensure that human opinions about the world will correlate to things as they actually are. It’s just as likely that our brains adapted to provide fitness advantages but failed to develop faculties capable of knowing the world independently of our mental biases. Philosophers often cite Darwin’s letter as evidence that he was aware of this unfortunate possibility.

In his book Where the Conflict Really Lies, Christian philosopher Alvin Plantinga argues that naturalism provides very little assurance that the belief content or opinions of human subjects are reliable mental impressions. Given naturalism of the sort Darwin and his modern day defenders promote, Plantinga asks, “what reason is there for supposing that this belief content [the convictions arrived at by human minds developed by unguided evolution] is true? There isn’t any. The neurology causes adaptive behavior and also causes or determines belief content: but there is no reason to suppose that the belief content thus determined is true. All that’s required for survival and fitness is that the neurology cause adaptive behavior; this neurology also determines belief content, but whether or not that content is true makes no difference to fitness.” Our brains may supply us fitness advantages, but these might come at the expense of truthful impressions of the world.

Secular philosopher Thomas Nagel agrees with Plantinga. In Nagel’s book Mind and Cosmos, he writes, “Mechanisms of belief formation that have selective advantage in the everyday struggle for existence do not warrant our confidence in the construction of theoretical accounts of the world as a whole. I think the evolutionary hypothesis would imply that though our cognitive capacities could be reliable, we do not have the kind of reason to rely on them that we ordinarily take ourselves to have in using them directly – as we do in science.” Naturalism can’t provide the necessary epistemological foundation to defend its own validity, and may in fact undermine itself by introducing the possibility that our knowledge of the material world is an illusion.

So what does this mean for naturalists and materialists, those who insist that every phenomenon in the universe can be reduced to expressions of chemistry, physics and mathematics? Both Plantinga and Nagel argue that we need a better explanatory model than the one naturalism provides if we are to continue placing trust in the knowledge science provides. Plantinga argues that theism offers the better alternative by positing a god who ensures that our mental impressions correspond to the world as it actually is, while Nagel rejects theism in favor of some yet discovered order in the universe. What is clear is that naturalism, and more specifically materialism, stands on shaky ground. Why then does it remain the prevalent worldview of academics and scientists?

Nagel offers a clue. He writes, “The priority given to evolutionary naturalism in the face of its implausible conclusions about other subjects is due, I think, to the secular consensus that this is the only form of external understanding of ourselves that provides an alternative to theism – which is to be rejected as a mere projection of our internal self-conception onto the universe, without evidence.” In other words, naturalists overlook the inadequacies of their worldview so long as it provides them an escape from theism. That hardly sounds like the objective, dispassionate response to data on which scientists pride themselves, does it?