Stephen Barr is probably my favorite science writer these days: he is both an authority in theoretical particle physics at the Bartol Research Institute at the University of Delaware, and an orthodox Roman Catholic who believes, as do I, that science and religion are not only compatible in the sense that they do not contradict each other, but they are, in the words of John Paul the Great, the two wings of human experience that together lift us to knowledge of the Good and the True. So I was particularly excited when the March number of First Things appeared in my mailbox today sporting a tidy little essay by Professor Barr entitled “Faith and Quantum Theory.”
The article presents an argument that I find quite congenial, having made a version of it myself over ten years ago (see Robert Brandon and Scott Carson, “The Indeterministic Character of Evolutionary Theory: No ‘No Hidden Variables’ Proof, But No Room for Determinism Either,” in Philosophy of Science 63 , pp. 315-337. The article is available online if you have access to JSTOR. Otherwise, you’ll just have to wait until the movie comes out). The upshot of both his and my articles: Determinism is dead. Not just dead as in, we can’t figure out how to make it work. Dead as in, it’s metaphysically not possible unless you’re willing to commit yourself to a metaphysics that is, in a word, insane.
Sometimes, when I teach the history of Presocratic philosophy, I will have students who ask questions about the metaphysical schemes of the Pythagoreans, questions about the viability of such schemes and about the very motivation behind seeing the world in the way that they did. If you’re not familiar with the Pythagoreans or their schemes, one aspect of their thought that has made them rather notorious is their proposal that the observable world is, in some sense, reducible to numbers or, as Philolaus proposed, known through numbers. To understand this proposal fully would require a rather detailed knowledge of ancient metaphysics and philosophy of mathematics, so I won’t go into more detail here. Suffice it to say that, when I get these questions from my students, I’m often tempted to point out that it is not all that different from what contemporary physicists are prone to do. We, too, represent the world numerically, particularly in the form of scientific equations but also in the form of predictions and explanations that are expressed in terms of probabilities.
Now, if you are a determinist, you view these probabilities as epistemic in nature. That is, if someone tells you that there is a 30 percent chance of rain tomorrow, if you are a determinist you think that what is meant by that is that, if only we knew everything there is to know about a particular weather system, down to the disposition of every last material particle, then we could say with 100 percent certainty whether it will rain tomorrow or not. But we cannot have that kind of complete knowledge of such a vast and complex physical system as the entire atmosphere of the earth, so our prediction reflects a certain amount of uncertainty on our part that is due to our lack of complete information.
There is another way to interpret probabilities, however, and it is much more congenial to both quantum mechanics and evolutionary theory. We may call this the metaphysical interpretation, because it posits that probabilities reflect, not limitations in our own knowledge of the physical universe, but the stochastic properties of a non-deterministic universe. That is, on the metaphysical interpretation of probabilities, we say that there is a certain chance that something will happen not because we do not know for sure what all of the variable are that will lead to one outcome rather than another, but because it is genuinely undetermined, at the time of our prediction, which outcome is going to take place.
Although he does not say much about this in his article, Professor Barr notes that this view of probability is congenial not only for quantum theory, but also for those who endorse the idea that the human will is free. As I mentioned in one of my earlier posts in this series, if the universe is a purely deterministic place, where materialism is the only correct metaphysics, then our wills cannot be free. So if you happen to believe that your will is free, it seems that you have to abandon either materialism or determinism. Some will want to abandon both, of course: the Christian must, in my view. But even if you are wedded to your materialism it might be time to dump that dinosaur, determinism.
We can’t, of course, take it for granted that our wills are free. Part of the point of these explorations of mine is to enquire into whether it is, in fact, possible to make any sense out of human freedom. It is worth emphasizing, however, that unless global determinism is false, we cannot be free. That is a controversial view (it was denied, for example, by Hume, and continues to be denied by the more dogmatic compatibilists), but I will not argue for it, since I doubt that many of my readers will find it all that problematic. In these matters, much depends upon one’s starting points.