Friday, April 20, 2007

Stephen Barr on Faith and Quantum Theory

The March issue of First Things is now available online without a subscription. One of the more interesting articles in that issue is an explanation of quantum theory and its implications for faith by Stephen Barr, a theoretical particle physicist at the Bartol Research Institute of the University of Delaware and the author of Modern Physics and Ancient Faith and A Student’s Guide to Natural Science.

The article includes a very readable and understandable explanation of quantum theory (which is quite an accomplishment). It then ends with a discussion of the implications of quantum theory on faith:


The Uncertainty Principle, the bedrock of quantum theory, implies that even if one had all the information there is to be had about a physical system, its future behavior cannot be predicted exactly, only probabilistically.


This last statement, if true, is of tremendous philosophical and theological importance. It would spell the doom of determinism, which for so long had appeared to spell the doom of free will. Classical physics was strictly deterministic, so that (as Laplace famously said) if the state of the physical world were completely specified at one instant, its whole future development would be exactly and uniquely determined. Whether a man lifts his arm or nods his head now would (in a world governed by classical physical laws) be an inevitable consequence of the state of the world a billion years ago.


But the death of determinism is not the only deep conclusion that follows from the probabilistic nature of quantum theory. An even deeper conclusion that some have drawn is that materialism, as applied to the human mind, is wrong. Eugene Wigner, a Nobel laureate, argued in a famous essay that philosophical materialism is not “logically consistent with present quantum mechanics.” And Sir Rudolf Peierls, another leading physicist, maintained that “the premise that you can describe in terms of physics the whole function of a human being . . . including its knowledge, and its consciousness, is untenable.”


There is much much more, and this article is worth reading in full. In particular, Barr offers a detailed explanation for his view that quantum theory means there is free will. Perhaps even more fascinating is his discussion of the various modern interpretations of quantum theory (Copenhagen interpretation, many-worlds interpretation, and Bohmian theory) and their different implications for faith:


What, then, are the philosophical and theological implications of quantum theory? The answer depends on which school of thought-Copenhagen, many worlds, or Bohmian-one accepts. Each has its strong points, but each also has features that many experts find implausible or even repugnant.

One can find religious scientists in every camp. Peter E. Hodgson, a well-known nuclear physicist who is Catholic, insists that Bohmian theory is the only metaphysically sound alternative. He is unfazed that it brings back Newtonian determinism and mechanism. Don Page, a well-known theoretical cosmologist who is an evangelical Christian, prefers the many-worlds interpretation. He isn’t bothered by the consequence that each of us has an infinite number of alter egos.

My own opinion is that the traditional Copenhagen interpretation of quantum theory still makes the most sense. In two respects it seems quite congenial to the worldview of the biblical religions: It abolishes physical determinism, and it gives a special ontological status to the mind of the human observer. By the same token, it seems quite uncongenial to eastern mysticism. As the physicist Heinz Pagels noted in his book The Cosmic Code: “Buddhism, with its emphasis on the view that the mind-world distinction is an illusion, is really closer to classical, Newtonian physics and not to quantum theory [as traditionally interpreted], for which the observer-observed distinction is crucial.”

Read it all.


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