Larry Moran, at Sandwalk, has argued that evolution is indeed a matter of chance. It is, he thinks, something that atheism requires. This is an interesting issue, one that has deep roots, both in the role of chance explanations in science and prescience, and the theistic reaction to it.
It’s perfectly okay to say, as a first approximation, that lots of evolution is random or accidental. This is a far closer approximation to the truth than saying it’s the all the result of design by natural selection.
What role does randomness or accident play here? Is it an explanation to say that things occur by accident, when they are what is to be explained? There are a number of meanings to “chance” in this case. One of them is that without a perturbing cause, ensembles of events will tend to form a Poisson Gaussian distribution – the “bell curve” of beginner’s statistics. If we don’t have something making things shift in one way or another, then many events of the same kind will cluster most densely around a value or location on the graph. Populations do this.
Another is that there are factors at work in any explanation that are not predicted by the theory used to explain. It is not, for example, predicted by the theory (or theories – I think there are at least 7 theories involved in evolutionary biology, but that’s another topic for another time) of evolution that there would be a bolide impact 65 million years ago. Once that happened, though, the theory predicts a general class of outcomes from a depauperated ecosystem.
But which lineages survived the Cretaceous bolide is also a kind of chance – called “contingency”. Some lineages may have survived because they happened to have biological features that permitted them to survive the impact winter that must have followed. Some, however, will have survived because they were in the right place at the right time.
Larry wants, I think from many emails exchanged and a conversation over drinks, to see that chance, accident, is a major “force” or factor in evolution. I think he means both unpredicted factors, and contingency. Deterministic factors like selection play a secondary role in his thinking.
I am reminded here of the Original Bad Boy for theists, right back to the time of Aristotle: Epicurus. Epicurus believed, more correctly as it turned out than Aristotle’s view, that what happens in biology and physics was caused by the internal dispositions of the atoms that made up living and physical things, in contrast to Aristotle’s finalism and formalism. But he had a problem explaining why things weren’t entirely the same everywhere and when. To “explain” this he supposed that originally (from eternity) atoms fell through the void (something else Aristotle rejected) in parallel paths, but that an accidental “swerve” brought them into collision from time to time, causing differentiation.
From this, theists, particularly Christian and Jewish theologians, attacked Epicurus as being atheist (which he may have been, but more likely thought the gods were too distant to effect change in the world), and holding that “everything was an accident”. In short, he removed meaning from the world by giving chance the centre stage. Actually, he didn’t, but chance did have a role in his scheme. Aristotle and the Stoics rejected this immediately, and Epicurean thinking diminished for around 2000 years.
The question here is about determinism and chance as competing explanatory strategies. If we accept a central role for chance in explanations, it is thought, then causality is at risk. Those who try for a strong selectionist or adaptationist account in evolution tend to be determinists. Those who, like Larry’s minor deity Gould, believe chance as contingency has a role tend to deprecate deterministic explanations.
In one sense, statistical explanation is a mixture of chance and necessity, as Jacques Monod called it famously. It is a necessary outcome that if no confounding cause intervenes, things will fall around a mode in a Poisson Gaussian distribution. I suspect that this astounding fact, which was called the Law of Error during the 19th century, is part of what drove Darwin’s thinking, although he was equally influenced by simple observation of variation in living things. But this is not the kind of chance in question – it is a causal fact of the world as we see it that things distribute that way.
Contingency, however, is not chance proper. A determinist could say quite happily that a theory doesn’t need to account for the boundary and initial conditions of the phenomena or process it seeks to explain, so long as some deterministic account can be given of them. In other words, we don’t need to think that bolides are created ex nihilo or that they swerve in an Epicurean sense to hit the earth in contradiction to orbital mechanics. Likewise, the changes in climate caused by the Milankovic cycle or the precession of the axis of the earth’s rotation, while not part of the theory of evolution, have predictable effects once they are included in the calculation. The “accident” here is just the fact of being extra-theoretical.
So when Larry says that atheists (by which he means the non-milksop nonbelievers in God who accept evolution as rational beings, not the milksop variety who refuse to make pronouncements on God… but we digress into already trodden ground) accept chance as a factor in evolution, I think there is a bit of trading on words rather than states of affairs. Yes, molecular changes can be “random” in the sense that they are external to the theory of evolution. They are not external to the theory of chemistry. In the domain of subatomic physics, the randomness of radioactive decay or gamma radiation has to do more with statistical properties than actual chance. The rates at which such events are caused or which have an effect on biological molecules are bounded. They aren’t wholly random.
All that said, is this a substantive disagreement between Larry and me? Not really, not in practice. We might think all of this, but still need to treat these events as random for the following reasons: no event occurs in anticipation of the future as it will be (not even when we plan for the future), but only in response to past events; and we do not ever act on, nor will we ever have, perfect information. All our real science has to factor in randomness because no matter how the universe may be – deterministic or stochastic – no theory, and no theoretician, can ever access all the information required. Determinism may be all very well as a philosophical dispute; it cannot be an operational part of science, not at the limit. Of course we must seek causal explanations, and they presuppose causality. There will be a point at which we have to treat noise in the data as an irreducible fact of our best theories, no matter how good those theories may get.
Theists will always kick up when chance gets mentioned, because they are the Überdeterminists. No small part of the created world can include real chance, because that is just contrary to doctrine. Atheists can allow there may be real chance, but I do not think they must. It is possible to be an atheist, milksoppish or not, and be a determinist at the post-quantum level. I think that determinism is the only metaphysics that makes sense of the world, but it is not a good standard for assessing theories or method.