Free will and Sabine Hossenfelder: what should the default, starting position be for a scientist?
Eying the Fruit Stand by John George Brown, 1884
Theoretical physicist, Sabine Hossenfelder believes that everything that happens in the real world, including our thoughts and decisions, are a consequence of the laws of nature and the initial conditions of the universe. On the basis of this a priori belief, she has argued that free will is an illusion.(1) As we shall shortly see, however, the rational justification for Hossenfelder’s belief logically collapses under her own assumption. Furthermore, thoughtful reflection indicates that the default, starting position for a scientist should be that we have free will.
The question of whether we have free will has enormous implications for our own humanity. This question goes right to the core of our significance and value as persons and has immense implications in every area of research, from psychology to theology to science.
Let us begin with two radically different options and see how well Hossenfelder’s belief holds up under rational thought.
Option one is a result of a belief known as scientific naturalism — the belief that the material world, consisting of space, time, matter, and energy, governed by physical laws, is all that exists. Under this option, free will is only an illusion. Instead, each ‘decision’ you make is actually a brain state caused by the determinate and indeterminate processes of the laws of nature working out from the initial conditions of the universe at the moment it began to exist
Option two takes it as self-evident that we can make meaningful decisions. These decisions are a consequent of rational deliberation, not merely the result of chemical reactions. Nature can certainly influence our deliberations, but we have the ability to consider what we naturally want to do versus what we ought to do, and override our natural desires and drives in order to make a decision that depends upon logical premises rather than chemical reactions.
Free will is commonly defined as your self-evident ability to make meaningful decisions that satisfy two criteria:
a) they are not caused by the laws of nature or anything other prior conditions and,
b) for every decision you make, you could have decided otherwise.
In order for free will to exist, there are two necessary requirements:
i) Scientific naturalism must necessarily be a false belief to satisfy criterion (a) and,
ii) To make decisions not determined by the laws of nature, we must have a mind that can perform logical and moral deliberation independent of the laws of nature, using the immaterial axioms of mathematics and logic, and choose between options. This ability to perceive and use immaterial axioms entails that there is, at the very least, an immaterial aspect to the mind.
So what should science’s default position be on the existence of free will?
Question: Can we even do science without the ability to make meaningful decisions about how to understand nature and set up experiments?
Sabine Hossenfelder’s a priori belief in scientific naturalism requires her to deny the existence of free will in the true libertarian sense. (1) Unfortunately, she unwittingly uses the basic laws of logic — something that is not governed by physics and chemistry — in her argument as to why she has decided that she cannot freely decide anything. The laws of logic are immaterial as well as foundational to reason and to all of physical reality. The laws of logic are not governed by the laws of nature. Thus, their very existence falsifies scientific naturalism. Let us clarify this more rigorously.
Since Hossenfelder accepts scientific naturalism, then everything that ever happens in the universe, including the brain-state that produced her belief in scientific naturalism, is a consequence of something we shall symbolize as ‘N’ — where, N represents, according to Hossenfelder, the initial conditions of the universe at the moment it began to exist, plus the laws of physics, including quantum mechanics, that govern how space, time, matter, and energy interact.
According to scientific naturalism then, everything that ever happens in the universe is a consequence of N.
But there is a major flaw …
The problem is that there are also people who believe that scientific naturalism is false. So, if we grant Hossenfelder’s belief in scientific naturalism, then N produces two, mutually contradictory beliefs. To clarify, N produces the belief that scientific naturalism is true and the belief that scientific naturalism is false. Recall that N represents the initial conditions of the universe and the laws of physics which govern it. Therefore, given her belief in scientific naturalism, N produces beliefs that are mutually contradictory at the same time in history. Since both beliefs cannot be true at the same time, we are left with the following two options.
Option 1: It is false that N determines our beliefs.
Option 2: ‘N’ is indifferent to whether the brain states it produces are true or false.
Because of Hossenfelder’s belief in scientific naturalism, she must deny Option (1), leaving only Option (2). It logically follows that if N produces brain states that are mutually contradictory, then N is indifferent to truth. But if this is the case, then her basis for believing that scientific naturalism is true, crumbles - it is merely a brain state determined by N, which is indifferent to the truth or falsity of the brain states it produces. To clarify, Hossenfelder’s belief in scientific naturalism results in the following:
All beliefs are a consequence of N.
At present, N has produced mutually contradictory beliefs about the truth of scientific naturalism (i.e., scientific naturalism is true and false)
If N produces mutually contradictory beliefs, then N is indifferent to truth.
Therefore, N is indifferent to truth.
It is important to understand premise (3). Saying that N is “indifferent to truth” means that the initial conditions of the universe at the instant it began to exist, and laws of physics which prescribe how the universe unfolds, are utterly irrelevant to the truth or falsity of the brain-states that N generates, which we call “beliefs”.
So here is the problem … Since Hossenfelder’s belief in scientific naturalism was the basis upon which she concluded that we have no free will, and if her belief in scientific naturalism has been produced by processes that are indifferent to truth, then her belief in scientific naturalism is no more valid than someone else’s belief that scientific naturalism is false, and the key assumption in her argument against free will collapses.
It gets worse: Since scientific naturalism entails that there is no immaterial reality, it is falsified if there is an immaterial reality that is foundational to science and the universe. Axioms are basic laws or truths that are foundational to mathematics and rational thinking. They govern material reality, the laws of physics, and the practice of science. Examples of these immaterial axioms include the law of non-contradiction, the law of identity, the principle of number, and the basic axioms of mathematics and geometry. These are not merely inventions of our mind; even if humans never existed, the axioms would still define all of reality, both material and immaterial.
Axioms are real, but they are also immaterial. By “immaterial” I mean they are not governed by the laws of nature, nor composed of matter or energy. They remain unchanged and timeless, and they are immune to any physical forces. For example, the law of non-contradiction is utterly unaffected by the extreme gravitational field on the surface of a neutron star, or the extreme temperatures inside a thermonuclear reaction, nor is it affected by the speed of light — nothing physical can affect an axiom, yet the axioms govern all of material reality. They are, therefore, immaterial, without mass or energy, and independent of space and time. The axioms are foundational to material reality, so they are very real. Given this, we can construct the following rational argument:
Whatever is presupposed by and governs the existence of material reality, the structure of the universe, and the practice of science, is more fundamental than all three.
The immaterial axioms of logic and mathematics are presupposed by and govern material reality, the structure of the universe, and the practice of science.
Therefore, the immaterial axioms of logic and mathematics are the foundation for material reality, the universe, and the practice of science.
Point: Material reality has a very real, immaterial foundation. Necessarily, this falsifies scientific naturalism. No scientist can deny the axioms and still practice science or even think rationally. The immaterial axioms of logic and mathematics do not arise out of the human mind, they govern material reality with, or without, human minds.
To summarize thus far: What we have done thus far is to snatch the rug out from under the feet of a scientist who assumes the truth of scientific naturalism, by:
a) showing that belief in scientific naturalism cannot be rationally justified if that belief is a result of N — which is indifferent to truth, and
b) pointing out that scientific naturalism is falsified by the existence of an immaterial foundation for material reality — the axioms of mathematics and logic we use to do science.
Free will defined
As mentioned earlier, a generally accepted definition for free will is as follows:
A decision is free if, and only if, it satisfies two conditions:
a) the decision was not determined by any prior conditions and,
b) the person could have decided otherwise.
You can likely see that criterion (a) rules out N as even a contingent cause of a free will decision. Criterion (b) shifts the responsibility for a decision away from N to the free will agent. By “free will agent” I mean any entity with a mind that has the attribute of free will.
Scientists and humans in general can certainly be influenced by any number of prior conditions, including N, but criterion (a) gives them the ability to intentionally override, set aside, or ignore those priors in their decision-making.
Observe that the ability to carry out a decision is not a criterion for free will. For example, a scientist might make a free will decision to gain academic prestige by fabricating the results of an experiment, but be subsequently exposed and discredited, failing in what he had decided to achieve. His initial decision was still free even though he failed to carry it out to completion.
So what are the starting options for a scientist?
Over my years in the halls of science, I have observed scientists choose between two different starting options in discussions of free will.
Option A: believe that we have no free will unless we can find evidence to support it, or
Option B: start with the hypothesis that we have free will, and test that hypothesis by attempting to falsify it.
If we were discussing the possibility of flying pigs instead of free will, then option (A) would be the obvious starting point, given the complete absence of any reason to believe in flying pigs or even to take the possibility seriously. In the same way, if there was zero evidence for free will — if it was a concept dreamed up by a writer of fantasy, then one could justify option (A) as the starting point.
There are at least two reasons why option (B) must be the default starting position for science.
First reason: Given our observation that it appears to us as if we have free will, a scientist, to be true to the scientific method, must recognize this as an observation. The observation might be mistaken in the end, but if our initial observation is that it appears to be self-evident to us that we have the ability to make meaningful, free decisions, then this constitutes an observation; thus, it would be absurd to claim there is no evidence for it.
An essential assumption that a scientist must make to practice science is that they are sane enough to not be intentionally self-deluding themselves about whether they have observed something or not. Most, if not all, scientists would grant that they observe within themselves what appears to be the ability to make meaningful, free will decisions on what choices to consider in the setup of experiments and the study of how nature works. Thus, the starting point for any scientist ought to be that since they observe themselves making what appears to be a continuous stream of free will decisions, and they are sane enough to not self-delude themselves into denying this observation; therefore, their default, starting position must be to accept the hypothesis that they have free will. Whether we actually have free will is not the same thing as accepting, as a working hypothesis, that we have free will.
Second reason: There is a second reason why the default starting position for a scientist must be that we have free will. Quite simply, every scientist uses it — or operates as if they can make meaningful decisions that are not merely physical brain states indifferent to what is true or false. To clarify, even Sabine Hossenfelder acts as if she possesses the ability to make meaningful choices in what she will research, what methodology she will use in her experiments, and how she will defend her findings to other scientists — not to mention deciding how she will attempt to logically argue that her free will decisions are an illusion. It appears she is using free will to argue that she has no free will.
It is one thing to assert that something is an illusion. It is quite another thing altogether, to make heavy use of the so-called illusion continuously day after day, while claiming to those all around them that it is just an illusion. If it seems self-evident that we have free will, and we use it continuously every day to make meaningful decisions, then the most rational default starting hypothesis for science to take is that free will exists and we use it all the time to make meaningful decisions.
This can be summarized with the following logical syllogism:
Scientists continuously observe what appears to be the ability to make meaningful, free will decisions, not determined by N, as they practice science.
Scientists not only observe this, but successfully operate as if they possess the ability to make meaningful decisions.
If (1) and (2), then the default hypothesis for science is that we possess the ability to make free will decisions that are not mere brain states determined by N.
Therefore, the default hypothesis for science should be that we have free will.
Falsifying the hypothesis:
Note that none of the above proves that we have free will — only that it ought to be the default starting position of science, and that it is a highly useful hypothesis in the daily practice of science and everything else. If a scientist wishes to reject this hypothesis of free will, on scientific grounds, they cannot merely invoke a philosophical belief in scientific naturalism — a philosophical belief is not science. Rather, they must falsify that hypothesis by experimentally testing a prediction arising out of the hypothesis.
The main competing hypothesis consistent with the belief in scientific naturalism is that the mind, including free will, is an ‘emergent’ property of the brain. In this context, the term emergent is a term used to imply scientific credibility when, in reality, we have not the foggiest idea how it is supposed to emerge. Nor have we any idea how an essentially material brain can perceive immaterial axioms and utilize them to infer abstract/immaterial logical and/or mathematical conclusions.
The free will hypothesis is that we have an immaterial mind that can perceive the immaterial axioms of logic and mathematics and actually use them to reason and arrive at conclusions not determined by N. The brain, therefore, is the interface between the mind and the material body. Damage the brain, and one damages the interface, severely impairing a mind’s ability to communicate and operate within the material body.
A “fly in the ointment”: If, in fact, we use free will to decide how to design an experiment to detect free will, we have the problem of free will ‘contaminating’ the experiment. As C.S. Lewis put it,
“All attempts to treat thought as a natural event involve the fallacy of excluding the thought of the man making the attempt.” (2)
A fundamental problem with Sabine Hossenfelder’s arguments (which use immaterial axioms of logic) is that she consistently assumes true, libertarian free will is doing no work in her thought processes since, she supposes, it cannot exist given her initial premise of scientific naturalism. Therefore, she does not have to worry about inadvertently using it in her rational deliberations, arguments, and experiments. An additional point relevant to trying scientific testing to detect free will - if free will and minds are immaterial, science might be the wrong tool to use. Science deals with the material — space, time, matter, and energy. Since free will must necessarily be an immaterial attribute if it is going to satisfy criterion (a) and avoid being determined by N, N-based science attempting to discover something that is not N-based is like using a hammer to detect the degree of emotive appeal in an oil painting. There might be a way, however, to falsify the hypothesis of free will.
Fundamental problem with the Libet experiments: Some experiments have been made on the brain to see if we can detect brain activity before the person can intentionally indicate their decision. These experiments, however, assume a brain-based property of free will — a compatibilist form of ‘free’ will that is actually an N-determined illusion. They also utterly fail to account for a model of how an immaterial mind with free will, if it exists, would interface with the brain. The reality is that these experiments are, unwittingly, perfectly consistent with a mind that interfaces with the brain and which must activate the brain in various locations in the process of fulfilling the requirements placed on the person by the experiment. Finally, it has been pointed out that these types of experiments do not test for meaningful decisions that involve rational deliberation and abstract thought. Instead, they focus more on simple reaction decisions that are more likely to be entirely within the normal operating mode of the physical, neural-network brain responding to external, physical stimuli. (3 - 5)
Applying the scientific method: The beauty of falsification is that it is especially useful in the real world where we cannot prove something with absolute certainty, but we can still apply the principle of falsification to a hypothesis to at the very least prove it is wrong.
Example: Consider the popular hypothesis that the mind, with its apparent ability to make free decisions, is an ‘emergent’ property of the brain. If the mind is merely an emergent property of the brain, then there are two testable predictions that can be made:
Prediction 1: If we split the brain into two independent brains incapable of communicating between them, we should observe two independent minds or persons.
Prediction 2: If we completely shut down the brain so it is physically incapable of functioning (i.e., no chemical or physical activity) we should also shut down the mind.
Conversely, if the mind exists independently of the brain, the opposite predictions can be made:
Prediction 1a: If we split the brain into two independent brains incapable of communicating between them, we should still observe one unified self-awareness and mind.
Prediction 2a: If we completely shut down the brain so it is physically incapable of functioning, the mind should be unaffected during that time.
The beauty of these two sets of predictions is that the falsification of one points to the verification of the other — an ideal situation in the scientific method.
Experimental results: The necessity of neurosurgery for a variety of medical conditions has resulted in the ethical testing of the above sets of predictions. For severe, chronic epileptic seizures, a split-brain procedure called a corpus callosotomy can greatly reduce or even end the ongoing seizures. In this procedure, the corpus callosum containing millions of nerve fibres connecting the left and right hemispheres of the brain, is split in half. After the operation, the two hemispheres of the brain function independently, with physical communication no longer possible between them. This procedure has been done thousands of times but, in every case, the person continued to have a single, unified sense of self-awareness and mind despite the resulting, left-right brain impairment of their physical perceptual abilities such as sight and speech. Their ability to perform abstract thought and reach deliberated, rational conclusions was utterly unaffected by the fact that they now possessed two independent brains.
In the words of neurosurgeon Michael Egnor,
“Like other neurosurgeons, I found no evidence either from ordinary clinical examination or events in their lives, that indicates their minds were split, even though their brains were.” (6)
This provides possible falsification of Prediction 1— falsifying the idea that the mind is an emergent property of the brain. At the same time, corpus callosotomies provide possible verification of Prediction 1a — the mind seems to exist independent of the brain or, in the case of those who have a split brain, unaffected by the fact that they possess two separate cerebra.
As for predictions (2) and (2a), those can be tested in the course of surgeries to remove aneurysms. The person’s body is chilled to 60 degrees F (15.6 degrees C), the heart is stopped, and the brain is drained of blood, while the brain is continuously monitored to confirm there is absolutely no chemical or physical activity occurring within it. Surprisingly, during this entire procedure, the person can often make corroborated observations that are physically impossible to make using their physical eyes, ears, and brain.
A wide variety of neurosurgeries consistently falsify the hypothesis that the mind is an emergent property of the brain. At the same time, they also continue to verify the hypothesis that the mind interfaces with the body through the brain and is the centre of a person’s self awareness and ability to perform abstract reasoning. The brain is a remarkable organ that effectively operates the innumerable ongoing functions of the body, but through extensive and highly detailed mapping of the brain through electrical probing, no part of the brain appears to be associated with abstract reasoning and conscious decision-making. The full range of neurosurgeries consistently reveal an independent self-awareness and capability to perform abstract thought and reasoning, which enables rational, meaningful decisions.
Summary point: In every way that we can test these hypotheses through a variety of neurosurgeries, the hypothesis that we have an immaterial mind capable of making free, meaningful decisions, continues to be verified. Conversely, in every way that we can test the hypothesis that the mind is an emergent property of the brain, through the full range of neurosurgical methods, the predictions are consistently falsified.
As a result, the starting hypothesis that we have free will continues to be the only hypothesis that survives the testing of its predictions. Therefore, the most rational working hypothesis is that we have an immaterial mind that possesses the attribute of free will. If the mind is immaterial, then it exists and operates independent of the laws of nature, which suggests that you are not just a body that has a mind. Rather, you may in fact be a mind that is clothed in a material body … but that is an idea for another discussion.
References:
Sabine Hossenfelder, “You don't have free will, but don't worry.” and “You don't have free will, but don't worry.”
C.S. Lewis, ’Bulverism’, God in the Dock.
Libet, Benjamin; Gleason, Curtis A.; Wright, Elwood W.; Pearl, Dennis K. (1983). "Time of Conscious Intention to Act in Relation to Onset of Cerebral Activity (Readiness-Potential)". Brain. 106 (3): 623–42.
Libet, Benjamin (1993). "Unconscious cerebral initiative and the role of conscious will in voluntary action". Neurophysiology of Consciousness. Contemporary Neuroscientists. pp. 269–306.
A. Schurger, A. Roskies, & U Maoz, ‘Neruoscientists should set a high bar for evidence against free will’, Scientific American, March 4, 2025.
M. Egnor & D. O’Leary, The Immortal Mind, 2025. In proper scientific methodology, Egnor systematically applies the results of a variety of neurosurgery procedures to essential predictions of the hypothesis that the mind is a material, ‘emergent’ property of the brain, showing how observations of specific neurosurgical procedures falsify that hypothesis while, at the same time, verifying the default hypothesis.
