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But Is Determinism True?

Does science show that we fated to want whatever we want?
 John Bell (1928–1990)
John Bell (1928–1990)

In a previous post, I argued that if determinism is true, we cannot have free will. That is, if everything we do is determined by the laws of physics and chemistry, there is no room for genuine freedom. In that respect, I am an “incompatibilist”—I don’t believe that free will is compatible with determinism.

What do I mean by determinism? Determinism, in the scientific sense intended here, is the view that for every moment in time, the state of the universe is completely determined by the state that immediately precedes it. If you knew all of the details of the universe — the location and state of every particle — at any given moment, you could know with certainty what comes next. Determinism is more or less the view that nature is a machine. If we know the position of the gears, we can know the future with certainty.

The question that naturally follows is this: Is determinism true? If so, free will is impossible in principle. If not, free will is possible.

It’s an interesting philosophical question, and most scientists (and ordinary folks) who have considered it seem to have decided that determinism is likely true. But they’re wrong.

In 1964, Irish physicist John Bell (1928–1990) published a paper titled “On the Einstein Podolsky Rosen Paradox”. In it, he observed that there is a way to test determinism at the quantum level by measuring the ratio of quantum states of particles emitted by radioactive decay.1 Bell’s experiment has now been done many times, and the answer is unequivocal: determinism at the quantum level is not true. Nature is not deterministic.

The experiments showed that every quantum process entails some degree of “indeterminism”; that is, there are predictable probabilities but there is never certainty. If we knew the exact state of the universe at any given moment, we could still never know with certainty what would happen next. Technically, this means that there are no local “hidden variables” which really govern how things happen, as many determinists (including Albert Einstein) had hoped.

Determinism in nature has been shown, scientifically, to be false. There is no real debate about this among physicists. So the question as to whether determinism, if it really existed, would be compatible with free will is merely an academic question, an interesting bit of metaphysical speculation.

Remarkably, modern theoretical and experimental physics, by decisively debunking determinism, is quite consistent with the view that libertarian free will is possible. It is not in any way ruled out by science.

The question that looms before us is no longer whether free will is compatible with determinism (compatibilism vs. incompatibilism) Rather, given the fact that nature is indeterminate, is it possible that human will is not free? If human actions are not determined by physics or chemistry, what besides free will could determine them? That’s the Next Big Question.

Physicist Brian Greene has a superb description of Bell’s theory and the experiments that followed on it in Chapter Four of The Fabric of the Cosmos.

Michael Egnor is a neurosurgeon, professor of Neurological Surgery and Pediatrics and Director of Pediatric Neurosurgery, Neurological Surgery, Stonybrook School of Medicine

Also by Michael Egnor: Can mere products of nature have free will?

Does brain stimulation research challenge free will?


Is free will a dangerous myth?

But Is Determinism True?