On free will-4: The implications of modern physics for determinism

(For previous posts in this series, see here.)

The possibility of the existence of Lucretian random swerves that destroy determinism received a boost in the early twentieth century with the advent of quantum mechanics and its associated uncertainty principle that eliminated strict classical determinism.

Believers in free will seized on the inherent randomness built into these newly discovered laws of nature to argue that free will could exist and manifest itself at the quantum level. However, as our understanding of quantum mechanics has increased, few scientists seriously accept this possibility anymore because of the many problems such a model has. After all, random processes are, well, random, meaning that they are not subject to being controlled. If indeterminancy at the quantum level is what undermines determinism, what we would have is not free will but what we might call ‘random will’, in the sense that we would be acting according to the random outcomes of quantum level phenomena over which we have no control. Furthermore, while individual quantum events may be completely indeterminate, they do obey laws that enable us to accurately predict statistical outcomes, so these events cannot be truly free. Free will as popularly conceived does not consist of random or statistically predictable behavior but of the ability to deliberate and determine specific outcomes. No mechanism has been proposed to suggest how that might occur.

Another feature of modern physics that has been floated as an escape route for free will is chaos theory. But chaos theory is strictly deterministic. What it says is that certain systems are so sensitive to the specification of their initial state, that the initial state can never be specified with sufficient accuracy to enable the prediction of final outcomes. So chaotic system are deterministic (hence do not allow for free will) but unpredictable. Furthermore, not all complicated systems are chaotic. Systems that are chaotic have to obey certain types of laws and it is not clear that the brain is a chaotic system.

The idea that free will can manifest itself by taking advantage of quantum uncertainty or chaos theory is an argument phrased in a vague form that currently only theologians and religious apologists take seriously, a desperate clasping at straws.

Biologist Anthony Cashmore summarizes the modern view that each one of us is a product of our genes (G), our environment (E), and a stochastic (random) component (S). (The Lucretian swerve: The biological basis of human behavior and the criminal justice system, Proceedings of the National Academy of Sciences, March 9, 2010, vol. 107, no. 10, 4499-4504.) The stochastic part comes from the randomness of events at the quantum level as well as those involved in things like genetic recombination, synapse formation, and so on. In other words, even identical twins (i.e., having the same G) reared in identical environments (E) will still have neuronal networks that differ due to this unpredictable stochastic contribution (S).

Cashmore points to the failure of advocates of free will to provide a mechanism to substantiate their belief.

Whereas much is written claiming to provide an explanation for free will, such writings are invariably lacking any hint of molecular details concerning mechanisms. Also, it is often suggested that individuals are free to choose and modify their environment and that, in this respect, they control their destiny. This argument misses the simple but crucial point that any action, as “free” as it may appear, simply reflects the genetics of the organism and the environmental history, right up to some fraction of a microsecond before any action.

To understand more deeply the issues involved, we need to understand the structure of the brain and how it works. An infant begins life with about 100 billion neurons (these are specialized nerve cells) in the brain, each with about 1000 links (called synapses) connecting it to other neurons, creating a complex interlocking web of neurons. The initial state of the brain is largely the product of our genes, though the environment in the form of the conditions in the womb undoubtedly plays a formative role as well. As the child grows, its life experiences result in a pruning of the number of neurons, the elimination of some synapses and the creation of new ones, resulting in each one of us having brains that have a unique neural network, shaped by genes and environment and the inherent randomness of the laws of nature. Even allowing for some attrition on the way to adulthood, the number of neurons and synapses we are left with is enormous, resulting in brains of immense power and complexity that dwarf even the most sophisticated computers of our age. It should not be surprising that the workings of the brain can be so subtle that it can create the illusion that it has powers in the form of a ghostly mind.

Given our modern understanding of the brain as a purely material entity, the widespread persistence of the strong belief in the existence of free will demands an explanation. It cannot be due entirely to social reasons such as needing the concept in order to assign responsibility for people’s actions. Like almost any feature that is ubiquitous among diverse populations (like the desire to believe in god), it is likely that susceptibility to belief in free will originated early in our evolutionary history and is hardwired in our brains because it has considerable survival value that has resulted in it being strongly selected for by natural selection. People who believe they have free will (even if this belief is false) are more likely to feel a sense of responsibility for their own actions and therefore less likely to do foolish and dangerous things, and thus more likely to survive and reproduce.

But while our powerful brains may be pre-disposed to believe in free will, it is also powerful enough to turn its analytical capacity to study its own workings. And as it does so, and our awareness of the power and complexity of the brain rises, it has started to undermine the notion of free will. But there is strong resistance to this trend, even among non-religious scientists. Cashmore says that while scientists are fairly open about their disbelief in a god, they tend to hedge their bets concerning free will, or at least are less reluctant to speak openly about the growing evidence that it likely does not exist. It is thought to be too explosive a topic, one that the general public might not be able to handle. Darwin himself seemed to feel that while there was likely no such thing as free will, it was better to keep this knowledge within the province of highly educated people who could deal with all its implications and not panic and go berserk.

Resistance to the idea that we do not have free will is likely to be far greater than the resistance Darwin encountered to his idea that human beings are, like any other species, just one of the products of evolution, nothing more. The idea of free will is not going to be given up except in the face of overwhelming evidence.

Next: Models of free will and the brain.


  1. Harry says

    Wonderful series, Dr. Singham!

    Respectfully, Cashmore’s argument appears to be rather tautological. Specifically:

    “This argument misses the simple but crucial point that any action, as “free” as it may appear, simply reflects the genetics of the organism and the environmental history, right up to some fraction of a microsecond before any action.”

    I read this as Cashmore saying words to the effect that, “actions are deterministic because actions are deterministic.”

    Your thoughts?

  2. Steve LaBonne says

    Harry, I read it as meaning “these are the factors that science tells us affect behavior. There’s no free will there. And there’s no additional factor that can be postulated which is compatible with the scientific worldview.” It could be refuted by adducing an example of such an additional factor which could enable the exercise of “free will”. So it’s not tautological.

  3. Linda says

    It seems to me that the far rightwing Nazi ideologue Heisenberg’s Interpretation of quantum mechanic laws had more to do with his philosophy than science. Causality and Determinism were labeled Communist philosophies (also known as Jewish Science to hide that the actual targets were the “left”) and right wing obscurantism ruled the day. http://www.marxist.com/quantum-mechanics-copenhagen130705.htm . I particularly appreciate the A bubble chamber photograph showing the
    paths of charged particles in a magnetic field which completely destroys the fascist Heisenbergs idealism/ obscurantist gibberish. Like Einstein, the socialist, I believe in strict determinism.
    PS Living in Rural Tennessee and being one who analyzes science, philosophy, and politics….being surrounded by rightwing uneducated bible thumpers who think faux News is the real deal………….makes me exclaim quite often “George Orwell was an optimist!”

  4. Harry says


    Thanks so much for your helpful response. However, I still struggle with reading Cashmore’s words as a tautology.

    Respectfully, “factors that affect behavior” is not the same as “factors that account for 100% of a behavior.” I am not aware of any scientific research that shows that the two factors Cashmore discusses, “genetics of the organism” and “environmental history” account for 100% of all behaviors.

    If you are aware of such research, I would be grateful if you would provide citations.

  5. says

    Good blog. You might want to check out my book, “The Scientific Worldview.” It starts out with the assumption that there is no free will and proposes “infinite universal causality”--a takeoff on Bohm (1957).


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