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Farewell to materialism and determinism Print
Guest column

Word on Fire
Brandon Vogt

This is the final article of a three-part series based on Brandon Vogt's discussion of text from the book, Modern Physics and Ancient Faith (University of Notre Dame Press, 2003) by physics professor Stephen M. Barr.

Twist #4 -- The mind as more than machine

If only matter exists, as the materialist thinks, then the human mind must be a machine. The invention and popularization of computers has made this idea even more plausible. Many people believe it is only a matter of time before computers become intelligent in ways that rival our own intelligence.

However, the past couple centuries have seen a bevy of arguments against the regnant view that the mind is no more than a physical machine -- a "wet computer" or "machine made of meat" as some have called it.

Barr covers some philosophical examples in his book, but the most impressive counterargument comes not from philosophy but from the science of computation itself.

It's based on a brilliant and revolutionary theorem proved in 1931 by the Austrian logician Kurt Gödel, and then built on by the philosopher John Lucas, and the mathematician Roger Penrose. Barr explains:

"The gist of the argument is that if one knew the program a computer uses, then one could in a certain precise sense outwit that program. If, therefore, human beings were computers, then we could in principle learn our own programs, and thus be able to outwit ourselves; and this is not possible, at least not as we mean it here."

Perhaps the only way to refute the Lucas-Penrose argument against the "machine mind", which leans on Gödel's Theorem, is to say that the human intellect reasons in a way that is inherently inconsistent. This would imply not just that human beings sometimes make logical mistakes (which is obvious), but that the human mind is radically and inherently unsound in its reasoning.

Yet that's a huge problem. Why? Because then to maintain the belief that your mind is only a machine, you would have to argue against your own mental soundness. You would literally identify as insane. Not many physicists are willing to go that far.

In any case, the discovery of Gödel's Theorem offers another blow to the materialist story of the world. It seems that the mind cannot be reduced to mere biochemical reactions.

Twist #5 -- The quantum  defeat of determinism

Most materialists deny that free will exists, and for centuries this seemed well-grounded in the findings of physics. The laws of physics appeared to be "deterministic," in the sense that what happens at a later time is solely determined through the laws of physics by what happened at earlier times. This was of course a troubling point for Judaism and Christianity, both of which held free will as a central tenant.

However, a truly astonishing reversal came in the 1920s with the discover of quantum theory. Barr describes it as "the greatest and most profound revolution in the history of physics" (27). It transformed the whole structure of theoretical physics, and in the process swept away physical determinism.

In prior centuries, the core of physical science was prediction. That's how theories were tested and proved. But with quantum theory, the present state of a physical system would not, even in principle, be enough to predict everything about its future behavior. No longer could you simply argue from the deterministic character of physics that free will was impossible.

Of course, this doesn't prove that we have free will. Instead, as Barr notes, "quantum theory simply showed that the most powerful argument against free will was obsolete. In the words of the great mathematician and physicist Hermann Weyl, 'the old classical determinism . . . need not oppress us any longer'" (27).

Opening the door to free will was one of the effects of quantum theory. In its traditional or "standard" interpretation, it also posits the existence of observers partially lie outside of the description provided by physics.

That's a controversial claim, and has been challenged by radical reinterpretations of quantum theory (such as the "many-worlds interpretation") or by altering the quantum theory.

Barr writes, "The argument against materialism based on quantum theory is a strong one, and has certainly not been refuted. The line of argument is rather subtle. It is also not well-known, even among practicing physicists. If it is correct, it would be the most important philosophical implication to come from any scientific discovery" (28).

The above represents just a sampling of the major discoveries in the great history of science and faith. Barr spends nearly 300 pages examining them in more depth. If you'd like to learn more, pick up a copy of Modern Physics and Ancient Faith for the rest of the discussion.


Brandon Vogt is a best-selling author, blogger, and speaker. He is the content director for Bishop Robert Barron's Word on Fire Catholic Ministries. He's the founder of ClaritasU, an online community for Catholics who want to get clear about their faith.