The Uncertainty Principle in Quantum Physics Does Not Mean We Have Free Will

Many people believe that things could have been different if they had acted differently in the past. If only they had made a different choice, such as choosing to accept a job opportunity, everything would have been better. This thought is based on the assumption that humans have free will. In other words, in the exact same situation, a person could have made a different choice.

The existence of free will would mean that the initial conditions of matter, both internal and external, would not be enough to determine a choice a person makes. If somehow an exact copy of our universe was made, this new universe would not necessarily progress in the same way ours does, as there are many possibilities for choices a person can make. These perceived options for action are not merely conceptions, but possible realities.

This is a flawed assumption, however, and humans are not able to make a multitude of choices in the same situation. Only one outcome is possible based on initial conditions. To change an outcome, the initial conditions must be changed, but for that to happen, the conditions that caused these initial conditions must be changed, and so on until you reach the beginning of time, if there is such a thing.

Determinism is the belief that all events, even those that occur in the human mind, are determined by causes outside one’s own will. Deterministic physical explanations of the mind and human behavior have greatly slimmed the possibility of an immaterial mind, often known as a soul. In the face of these physical theories of the mind, proponents of free will have begun to argue that quantum uncertainty allows for the possibility of free will. If aspects of the brain are influenced by quantum particles, then the brain is somewhat undetermined and unpredictable in which space lies the possibility for freedom, a believer in free will might argue.

This relies on a misinterpretation of quantum physics, however, as although the formulas relating to quantum mechanics do imply a sort of probabilistic randomness, that is because of the limits of human knowledge on quantum particles, especially the Heisenberg Uncertainty Principle. These limitations prevent us from accurately describing and predicting the movement of quantum particles. This does not imply a lack of causation that allows for infinite possibilities, however. They instead show that there are limitations that prevent scientists from accurately predicting and describing the determinism of the universe, not that the universe is undetermined.

The Heisenberg Uncertainty Principle states that the position and velocity of a quantum particle cannot both be known with complete accuracy. As the velocity of a quantum particle is known with increasing certainty, the position of the particle is known with decreasing certainty, and vice versa. This is not because a conscious creature is observing the particle which causes the particle to change its behavior, which is a common misconception.

Whether or not a person observes the data made available by recording instruments does not change what the particle does. Rather, the instruments recording the properties of a particle must interact with the particle to record some of its properties, thus changing the particle’s properties. For example, an electromagnetic wave with a wavelength similar to the size of a quantum particle may be shot at the particle, and the way this wave interacts with the particle indicates information about its position or velocity with some uncertainty. Unless both the position and velocity of a quantum particle were known with complete certainty beforehand, the outcome of observing the particle with measuring devices cannot be known.

All properties of a quantum particle cannot be discovered with relative certainty in the same measurement, and observing a particle with scientific instruments will change those properties since electromagnetic waves and particles have momentum. Based on these two principles and our current understanding of quantum mechanics, it seems that scientists will never be able to know a particle’s properties with complete certainty and perfectly describe what influences the particle’s movement.

Uncertainty does not imply a lack of deterministic causation, however. As I argued in a previous essay, the appearance of randomness does not necessarily mean an event was undetermined. The outcome of a roll of a die is considered random by most, but thrown in the same way again and again under the same conditions a die would land on the same side every time, at least according to the general understanding of physics. This assumption made by classical physicists seems to almost certainly be true, as an experiment can be performed multiple times with extremely similar results every single time, and slight deviation could conceivably be due to many possible factors that cannot be eliminated. The reason deviations from predictions at the quantum level are said to be due to the inherent randomness and indeterminism of quantum particles is because scientists cannot prevent or understand hidden factors at that level. In a sense, if we cannot predict the outcome of an event with any certainty at all it might as well be random in our perceptions of the event, but that does not make it random in reality.

The human throwing the die does not have the precision nor calculative abilities to ensure and predict the result of the die roll before it happens, but a robot possibly could. A die, although following the laws of quantum mechanics, is so massive that all properties of the die can be known with a negligible amount of uncertainty. This uncertainty is so minuscule that classical physics is a very accurate predictor of the die’s motion, and for the majority of its existence, Newtonian physics was so accurate that there was little reason to question it.

When it comes to observing and describing particles with miniscule mass such as electrons, and even some particles which seem to have no mass, Newtonian physics comes apart. With this switch from Newtonian physics to quantum physics, the door seemed to open for those who hope that humans are free to make any possible choice. These people argue that due to scientists’ inability to predict movement at the quantum level, such particles must move in random ways. These particles then interact with the human brain, creating room for free will.

It is true that the state of quantum particles cannot be known with complete certainty, and these states can even superimpose upon each other causing further confusion, but that does not mean any outcome is possible. This just means that scientists cannot know what the outcome of a quantum particle’s movement or decay will be until it happens, similarly to how you do not know how a die will land when you throw it. How the die lands depends on how it collides with the table, and based on these bounces and how it was thrown it lands on a certain side.

The Shrodinger’s Cat thought experiment is a great example of the absurdity of this misconception. In the experiment, Schrodinger supposes there is a cat in a box, and along with this cat, there is a quantum particle with superimposed states and a Geiger counter that will either release poison into the box or do nothing depending on how the particle decays. Some people would argue that the cat is both dead and alive before the box is opened because the outcome of the decay is unknown. The fate of the cat is unknown and therefore undetermined until the box is opened and the state of the cat is observed.

The cat is definitely either dead or alive even before the box is opened, however. Just because the quantum particle could conceivably decay into two possible states does not mean the cat could in reality be dead or alive until an observer chooses to open the box. There is not enough information available about the particle to predict its outcome. There is only enough information to outline two conceivable outcomes. This does not mean that both options are possible, as only one outcome will occur. There is only one possible outcome based on the initial circumstances. We simply cannot know the initial circumstances and therefore it is assumed that any option could potentially happen, but that is a faulty assumption.

The human mind is almost certainly completely material, meaning that the brain and all physical processes that occur in the nervous system of the human body are the sole sources of consciousness. Ever since the conception of psychology and neuroscience, physical explanations for the mind have increased in both depth and accuracy. With the advancement of the mental sciences, we no longer have to rely on explanations of the mind that assume a divine nature to human thought that falsely elevate humanity over our nonhuman counterparts.

For the mind to be free from deterministic causation it would have to be composed of something that is not subject to the laws of physics, such as an immaterial soul as René Descartes argued. The existence of an immaterial soul that even slightly influences the mind is a decreasing likelihood. As there is no solid evidence which should lead us to believe in an immaterial soul in the first place, I believe it is safe to assume that there is no such thing or at least that it has no influence on cognition, and therefore humans do not have free will in the sense that I mean.

Compatibilists may argue that the term ‘free will’ has a different definition, and therefore free will and the determinism of material things are compatible. Many of these compatabilists argue that free will should mean the absence of physical or other such threats or restraints that would prevent a person from making the choice they want. In this sense, a person is unfree if another person is holding a gun to their head forcing them to do things, or if someone is threatening to take away their job if they don’t act as the other person wants. Being unfree would mean not having the capacity to act in a way you want, either due to physical inability or a perceived necessity coercing you to go against your desires.

This definition of free will aligns with the average person’s conception of freedom of action, but I do not believe this is what is usually meant by the term ‘free will’. Free will is most often used to mean the ability for a person to make any choice in a specific situation. If free will is taken to mean freedom to act and choose according to a person’s will, then yes, humans are often free. This definition does not change the fact that the human mind is subject to physical causation, and therefore what happens must still necessarily happen. There is only one possible choice a person can make in a situation, no matter how much they feel otherwise.

If ‘free will’ is taken to mean freedom from the determinism that applies to everything material, then humans almost certainly have no free will. As quantum mechanics teaches us about the physical, there is no such thing as absolute certainty, only the reduction of uncertainty to a negligible level. I believe the possibility of free will to be as negligible as the effect of the uncertainty principle on recording the properties of a large object.

The choices and conditions of humans are determined by the laws of physics, whether currently described by science or not. Your fate is not necessarily bad or good, and is likely not decided by a conscious entity. It simply is. Whatever happens is necessitated by physical interactions, whether outside of your mind, inside your mind, or both. Making choices other than those you do is impossible except in your imagination, as different choices cannot be made unless conditions influencing the choice are different. Believing you should have done differently is not useless, as this reflection can make you a better person in the future, but it is impossible to go back in time and change your actions. It is equally impossible for you to have made a different choice in the moment, no matter how foolish or despicable it may have been.

Further Reading/ Sources:

Visualization of Quantum Physics (Quantum Mechanics)

The Uncertainty Principle (Stanford Encyclopedia of Philosophy)

What did Schrodinger’s Cat experiment prove? | Science Questions with Surprising Answers.


Why Everything You Thought You Knew About Quantum Physics is Different — with Philip Ball



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Justin Bowen

Justin Bowen


My name is Justin Bowen and I’m currently living in the state of Georgia in the United States. I’m interested in philosophy, history, psychology, and literature