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See Inside Scientific American Mind Volume 23, Issue 2

How Physics and Neuroscience Dictate Your "Free" Will

Physics and neurobiology can help us understand whether we choose our own destiny



Photoillustration by Aaron Goodman

In Brief

  1. Most of us believe that we are free because, under identical circumstances, we could have acted otherwise. Determinism—the idea that all particles in the universe follow set trajectories—challenges this idea.
  2. Theories to explain the potential origins of free will draw on physics, including Heisenberg’s uncertainty principle.
  3. Whether or not free will exists, psychology and neuroscience are beginning to explain why we feel as if we can influence our destiny.

In a remote corner of the universe, on a small blue planet gravitating around a humdrum sun in the outer districts of the Milky Way, organisms arose from the primordial mud and ooze in an epic struggle for survival that spanned aeons.
Despite all evidence to the contrary, these bipedal creatures thought of themselves as extraordinarily privileged, occupying a unique place in a cosmos of a trillion trillion stars. Conceited as they were, they believed that they, and only they, could escape the iron law
of cause and effect that governs everything. They could do this by virtue of something they called free will, which allowed them to do things without any material reason.

Can you truly act freely? The question of free will is no mere philosophical banter; it engages people in a way that few other metaphysical questions do. It is the bedrock of society’s notions of responsibility, praise and blame. Ultimately it is about the degree of control you exert over your life.

Let’s say you are living with a loving and lovely spouse. A chance meeting with a stranger turns this life utterly upside down. You begin talking for hours on the phone, you share your innermost secrets, you start an affaire de coeur. You realize perfectly well that this is all wrong from an ethical point of view; it will wreak havoc with many lives, with no guarantee of a happy and productive future. Yet something in you yearns for change.

Such gut-churning choices confront you with the question of how much say you really have in the matter. You feel that you could, in principle, break off the affair. Despite many attempts, you somehow never manage to do so.

In my thoughts on these matters of free will, I neglect millennia of learned philosophical debates and focus on what physics, neurobiology and psychology have to say, for they have provided partial answers to this ancient conundrum.

Shades of Freedom
I recently served on a jury in United States District Court in Los Angeles. The defendant was a heavily tattooed member of a street gang that smuggled and sold drugs. He was charged with murdering a fellow gang member with two shots to the head.

As the background to the crime was laid out by law enforcement, relatives, and present and past gang members—some of them testifying while handcuffed, shackled and dressed in bright orange prison jumpsuits—I thought about the individual and societal forces that had shaped the defendant. Did he ever have a choice? Did his violent upbringing make it inevitable that he would kill? Fortunately, the jury was not called on to answer these irresolvable questions or to determine his punishment. We only had to decide, beyond a reasonable doubt, whether he was guilty as charged, whether he had shot a particular person at a particular place and time. And this we did.

According to what some call the strong definition of free will, articulated by René Descartes in the 17th century, you are free if, under identical circumstances, you could have acted otherwise. Identical circumstances refer to not only the same external conditions but also the same brain states. The soul freely chooses this way or that, making the brain act out its wishes, like a driver who takes a car down this road or that one. This view is the one most regular folks believe in.

Contrast this strong notion of freedom with a more pragmatic conception called compatibilism, the dominant view in biological, psychological, legal and medical circles. You are free if you can follow your own desires and preferences. A long-term smoker who wants to quit but who lights up again and again is not free. His desire is thwarted by his addiction. Under this definition, few of us are completely free.

It is the rare individual—Mahatma Gandhi comes to mind—who can steel himself to withhold sustenance for weeks on end for a higher ethical purpose. Another extreme case of iron self-control is the self-immolation of Buddhist monk Thich Quang Duc in 1963 to protest the repressive regime in South Vietnam. What is so singular about this event, captured in haunting photographs, is the calm and deliberate nature of his heroic act. While burning to death, Duc remained in the meditative lotus position, without moving a muscle or uttering a sound, as the flames consumed him. For the rest of us, who struggle to avoid going for dessert, freedom is always a question of degree rather than an absolute good that we do or do not possess.

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