Professor Emeritus, Department of Ecology and Evolution, University of Chicago; Author, Why Evolution is True; Faith Versus Fact: Why Science and Religion are Incompatible.

A concept that everyone should understand and appreciate is the idea of physical determinism: that all matter and energy in the universe, including what’s in our brain, obey the laws of physics. The most important implication is that is we have no “free will”: At a given moment, all living creatures, including ourselves, are constrained by their genes and environment to behave in only one way—and could not have behaved differently. We feel like we make choices, but we don’t. In that sense, “dualistic” free will is an illusion.

This must be true from the first principles of physics. Our brain, after all, is simply a collection of molecules that follow the laws of physics; it’s simply a computer made of meat. That in turn means that given the brain’s constitution and inputs, its output—our thoughts, behaviors and “choices”—must obey those laws. There’s no way we can step outside our mind to tinker with those outputs. And even molecular quantum effects, which probably don’t even affect our acts, can’t possibly give us conscious control over our behavior.  

Physical determinism of behavior is also supported by experiments that trick people into thinking they’re exercising choice when they’re really being manipulated. Brain stimulation, for instance, can produce involuntary movements, like arm-waving, that patients claim are really willed gestures. Or we can feel we’re not being agents when we are, as with Ouija boards. Further, one can use fMRI brain scans to predict, with substantial accuracy, people’s binary decisions up to ten seconds before they’re even conscious of having made them.

Yet our feeling of volition—that we can choose freely, for instance, among several dishes at a restaurant—is strong: so strong that I find it harder to convince atheists that they don’t have free will than to convince religious believers that God doesn’t exist. Not everyone is religious, but all of us feel that we could have made different choices.

Why is it important that people grasp determinism? Because realizing that we can’t “choose otherwise” has profound implications for how we punish and reward people, especially criminals. It can also have salubrious effects on our thoughts and actions.   

First, if we can’t choose freely, but are puppets manipulated by the laws of physics, then all criminals or transgressors should be treated as products of genes and environments that made them behave badly. The armed robber had no choice about whether to get a gun and pull the trigger. In that sense, every criminal is impaired. All of them, whether or not they know the difference between right and wrong, have the same excuse as those deemed “not guilty by reason of insanity.”

Now this doesn’t mean that we shouldn’t punish criminals. We should—in order to remove them from society when they’re dangerous, reform them so they can rejoin us, and deter others from apeing bad behavior. But we shouldn’t imprison people as retribution—for making a “bad choice.” And of course we should still reward people, because that rewires their own brains, and those of onlookers, in a way that promotes good behavior. We can therefore retain the concept of personal responsibility for actions, but reject the idea of moral responsibility, which presumes that people can choose to do good or bad.

Beyond crime and punishment, how should the idea of determinism transform us? Well, understanding that we have no choices should create more empathy and less hostility towards others when we grasp that everyone is the victim of circumstances over which they had no control. Welfare recipients couldn’t have gotten jobs, and jerks had no choice about becoming jerks. In politics, this should give us more empathy for the underprivileged. And realizing that we had no real choices should stave off festering regrets about things we wished we had done differently. We couldn’t have.  

Many religions also depend critically on this illusory notion of free will. It’s the basis, for instance, for Christian belief that God sends people to heaven or hell based on whether they “choose” to accept Jesus as their savior. Also out the window is the idea that evil exists because it’s an unfortunate but necessary byproduct of the free will that God gave us. We have no such will, and without it the Abrahamic religions dissolve into insignificance.

We should accept the determinism of our behavior because, though it may make us uncomfortable, it happens to be true—just as we must accept our own inevitable but disturbing mortality. At the same time, we should dispel the misconceptions about determinism that keep many from embracing it: that it gives us license to behave how we want, that it promotes lassitude and nihilism, that it means we can’t affect the behavior of others, and that embracing determinism will destroy the fabric of society by making people immoral. The fact is that our feeling that we have free will, and our tendency to behave well, are so strong—probably partly ingrained by evolution—that we’ll never feel like the meat robots we are. Determinism is neither dangerous nor dolorous.

There are some philosophers who argue that while we do behave deterministically, we can still have a form of free will, simply redefining the concept to mean things like “our brains are very complex computers” or “we feel we are free.” But those are intellectual carny tricks. The important thing is to realize that we don’t have any choice about what we do, and we never did. We can come to terms with this, just as we come to terms with our mortality. Though we may not like such truths, accepting them is the beginning of wisdom.