Over the past year or so, two very interesting books in the philosophy of nature have attracted attention outside of the ultra-rarefied world of academic discourse: Alex Rosenberg’s The Atheist’s Guide to Reality: Enjoying Life without Illusions and Thomas Nagel’s Mind and Cosmos: Why the Materialist Neo-Darwinian Conception of Nature Is Almost Certainly False. Both of these works have been extensively discussed in popular magazines, radio shows, blogs, and esp. at Uncommon Descent. Here, I want to briefly describe what I see going on here and open up the topic for critical discussion.
Rosenberg’s central claim is that “the physical facts fix all the facts” — all the sociological, psychological, biological, and chemical facts that there are, are determined by the facts about fermions and bosons. Anything that cannot be explained in terms of bosons and fermions just is not the case. This means that there is no such thing as intentionality, teleology (purposiveness), or meaning — not really. These notions turn out to be nothing more than cognitive short-cuts that our distant ancestors evolved in order to survive on the African savannah of the lower-to-mid Pleistocene. Intentionality is no obstacle for Rosenberg’s naturalism, because there’s just no such thing. (Interestingly, he does concede that mathematics is a problem for naturalism — why he makes the concession for mathematics, but not for intentionality, puzzles me greatly.)
Nagel, by contrast, takes the opposite view: that the unquestionable reality of intentionality and consciousness strongly suggests that disenchanted naturalism — Rosenberg-style naturalism — simply cannot be the whole story. What he proposes instead is what he wants to call “natural teleology”: that there is a basic tendency at work in the cosmos towards living things with intentionality and consciousness.
Rosenberg insists that intentionality teleology cannot be naturalized; Nagel insists that they must be. But it is not really clear what “natural teleology” might mean, or whether intentionality could be naturalized. So that’s what I want to explore a bit further.
On one common interpretation, intentionality and teleology require that there be “final causes”. And final causes seem to be the sort of thing that the scientific revolution dispensed with — that’s what it means to say that the modern conception of nature is “disenchanted”. But while it’s certainly true that the scientific revolution showed the uselessness of final causation for doing physics (and maybe chemistry), I submit that the scientific revolution did not show the uselessness of final causes for biology (let alone psychology. etc.) So there’s one way of understanding the irreducibility of biology to physics: biology requires final causes, and physics does not.
However, that seems inadequate, because we still want to know where final causation, or purposiveness, comes from. (This is the ‘hard problem’ that makes the problem of the origin of life seem so intractable.) How can we naturalize final causes without reducing final causes to efficient causes? (I’m open to different ways of framing the problem than this one, of course.)
A provisional solution: final causes can be explained in terms of efficient causes. “Wait a minute!”, one might say, “doesn’t that just reduce them to efficient causes, in that case?” And to that my answer is “no.” We would be reducing final causes to efficient causes if we showed that we could replace all talk of final causes with talk of efficient causes, without suffering any loss of predictive success or explanatory power. But that’s a kind of conceptual analysis — whereas what I’m talking about is explaining final causes in terms of efficient causes, which is not a matter of rejecting final causes or eliminating them from our scientific world-view, but a matter of showing how to make sense of final causes — which are, I submit, indeed indispensable for biological and psychological explanations — within the modern scientific world-view.
Nature can be, perhaps, partially re-enchanted after all.