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Does Science Disprove Free Will? A Physicist Says No

Marcelo Gleiser notes that the mind is not a solar system with strict deterministic laws

One of the most disturbing implications of materialism in modern science is the inference that science disproves the existence of free will. Of course, this is not actually the case, but even the mistaken denial of free will has profound and very disturbing implications for our social structure, our criminal justice system, and our way of government. People who are assumed to lack free will are ultimately little more than cattle to be herded and, as philosopher Hannah Arendt has observed, the denial of free will — and the denial of individual responsibility that follows on it — is a cornerstone of totalitarianism.

Marcelo Gleiser

At Big Think, physicist and philosopher Marcelo Gleiser points to the fallacy that physics and neuroscience disprove free will:

[T]he mind is not a solar system with strict deterministic laws. We have no clue what kinds of laws it follows, apart from very simplistic empirical laws about nerve impulses and their propagation, which already reveal complex nonlinear dynamics. Still, work in neuroscience has prompted a reconsideration of free will, even to the point of questioning our freedom to choose. Many neuroscientists and some philosophers consider free will to be an illusion. Sam Harris, for example, wrote a short book arguing the case.

Marcelo Gleiser, “Do the laws of physics and neuroscience disprove free will?” at Big Think (November 10, 2021)


The argument against free will is based on several mistaken assertions. The first mistake is the assertion that nature is deterministic — that changes in the natural world are completely determined by the state of affairs immediately prior to the change, and therefore we cannot make free choices because our choices are determined by our brain state immediately prior to the choice. However, research in physics involving Bell’s theorem over the past half century clearly indicates that, at the quantum level, nature is not deterministic, at least not in a local sense. Determinism in physics is an erroneous assumption, and therefore any inference that physical determinism disproves free will is based on an erroneous assumption.

The second mistake is a failure to see that the denial of free will is self-refuting. If our thoughts and actions are wholly determined by physical processes, then our thoughts and actions cannot be assertions of truth — physical processes are not propositions. If our mental states are wholly determined by our physical brain states, we have no reason to ascribe “truth” to any mental state.

Gleiser points out a third mistake — misinterpretation of neuroscience research on free will:

This shocking conclusion [that free will is an illusion] comes from a series of experiments that revealed something quite remarkable: Our brains decide a course of action before we know it. Benjamin Libet’s pioneering experiments in the 1980s using EEG and more recent ones using fMRI or implants directly into neurons found that the motor region responsible for making a motion in response to a question fired up seven seconds before the subject was aware of it. The brain seems to be deciding before the mind knows about it. But is it really?

The experiment has been debunked, which actually is far from surprising. But what was surprising was the huge amount of noise that the claims against free will emerging from this type of experiment generated. To base the hefty issue of free will on experiments that measure neuronal activity when people move fingers to push a button should hardly count as decisive. Most of the choices we make in life are complex, multi-layered decisions that often take a long time.

Marcelo Gleiser, “Do the laws of physics and neuroscience disprove free will?” at Big Think (November 10, 2021)


Libet’s conclusion that conscious decision-making was preceded by a half second of unconscious brain activity has been shown to be an error. The brain activity recorded by Libet and by other investigators who followed him appears to represent nonspecific “noise” in neuronal networks that is associated with the mental state leading up to making a simple choice. More detailed research has shown that the brain activity most highly correlated with decision-making happens simultaneously with the awareness of the choice. There is no neuroscientific reason to doubt the reality of free will.

Gleiser concludes:

This should be a relief to most people, for many reasons. First, we are definitely not automatons without choice. Second, we actually do need to take responsibility for our actions, from wasting water in a long shower to shooting someone dead. There is no cosmic machinery making us do stuff, one way or the other. This means that we must face up to the way we live our lives and how we relate to each other and to the planet, knowing that our choices do have consequences that go beyond our small bubble of being.

Marcelo Gleiser, “Do the laws of physics and neuroscience disprove free will?” at Big Think (November 10, 2021)


Our current state of physics and neuroscience is entirely consistent with the inference that free will is real. Our choices are not determined by our brain states or by our environment. Of course, we are influenced by a variety of factors, but under most circumstances we can freely choose our actions.

Without free will, we cannot be subject to moral law. Yet virtually all human beings continuously feel the weight of moral reasoning. Gleiser is right to point out that the physics and neuroscience of the 21st century clearly support the reality of free will — the reality of the ongoing efforts to “do the right thing” — that we all feel in our daily lives.

Note: Another theoretical physicist disagrees. See: Can physics prove there is no free will? No, but it can make physicists incoherent when they write about free will. It’s hilarious. Sabine Hossenfelder misses the irony that she insists that people “change their minds” by accepting her assertion that they… can’t change their minds. (Michael Egnor)


Michael Egnor

Senior Fellow, Center for Natural & Artificial Intelligence
Michael R. Egnor, MD, is a Professor of Neurosurgery and Pediatrics at State University of New York, Stony Brook, has served as the Director of Pediatric Neurosurgery, and award-winning brain surgeon. He was named one of New York’s best doctors by the New York Magazine in 2005. He received his medical education at Columbia University College of Physicians and Surgeons and completed his residency at Jackson Memorial Hospital. His research on hydrocephalus has been published in journals including Journal of Neurosurgery, Pediatrics, and Cerebrospinal Fluid Research. He is on the Scientific Advisory Board of the Hydrocephalus Association in the United States and has lectured extensively throughout the United States and Europe.

Does Science Disprove Free Will? A Physicist Says No