Quantum Physics and Mental Causation

Quantum Physics and Mental Causation

By Robert O. (“Bob”) Doyle

A paper prepared for a conference on Quantum Physics and the Philosophy of Mind, Milan, Italy, June 4-6, 2013.

Abstract:

The problem of mental causation depends heavily on the idea of “causal closure” of the world under deterministic laws of nature. The central question in the classic mind-body problem is how can an immaterial mind move a material body if the “causal chains” are limited to interactions between physical things.

We propose a model or theory of mind as the pure information in the biological information-processing system that is the brain and central nervous system. We show how this model can support a non-reductive physicalism. Information is physical, but immaterial. Quantum physics produces breaks in the strict “causal chains” that have been used to “reduce” biological phenomena to physics and chemistry and mental events to neural events. But statistical causes remain.

Biological information processors are quite different from the digital computers analogized in computational theories of mind.

We argue against neurobiological reductionism and strictly determined “bottom-up causation.” At the same time, we defend a supervenient statistical “downward causation” that allows free thoughts (mental events that are not pre-determined) to cause willed actions. Actions are ultimately statistical but “adequately determined” by our motives, reasons, intentions, desires, and feelings, in short, by our character.

Introduction:

Quantum mechanical events have generally been thought to be unhelpful by philosophers of mind. Adding indeterminism to mental events apparently would only make our actions random and our desires the product of pure chance. If our willed actions are not determined by anything, they say, we are neither morally responsible nor truly free. Whether mental events are reducible to physical events, or whether mental events can be physical events without such a reduction, the interposition of indeterministic quantum processes apparently adds no explanatory power. And of course if mental events are epiphenomenal, they are not causally related to bodily actions. Epiphenomenal access to quantum physics would not help.

[Some philosophers of mind (e.g., John Searle David Chalmers Christoph Koch?) have considered the “mystery” of quantum indeterminism as potentially relevant to philosophy of mind, for example specifically to the problem of consciousness, because it too is a “mystery. “ But explaining one mystery with another mystery is questionable, at best.]

Our challenge is to admit some quantum indeterminism into a “statistical” causality (an indeterminism which renders our mental causes merely “statistical”) yet nevertheless allow us to describe mental causes as “adequately determined.” That is to say, mental causes are essentially - and for all practical purposes - “determined,” because the statistics in most cases are near to certainty. Even more importantly, our thoughts - and subsequent actions – are in no way completely “pre-determined,” neither from causal chains that go back before our birth such as our genetic inheritance, nor from the immediate events in the “fixed past,” which together with assumed deterministic “laws of nature,” are thought by most compatibilist philosophers to completely explain our actions.

In part I of this paper we explore a mental causation model of non-reductive physicalism that treats the mind as physical, but nevertheless immaterial. Specifically, we identify the mind as the information in a brain. We regard the brain and central nervous system as a biological information-processing system, one that has very little in common with the computational brain models of today’s cognitive science.

Information is immaterial. It is neither matter nor energy, although it needs matter for its (temporary) embodiment and energy for its communication - for example to other minds or for storage in the external environment.

In part II, we review the arguments for quantum mechanical indeterminism and show how quantum physics introduces indeterminism into the motions of the fundamental particles, making their motions stochastic and their future positions statistical, not certain.

Indeterminism breaks critically located links in the “causal chains” that have historically been used by philosophers of mind to argue for “bottom-up” causation. Breaking these deterministic links means that the properties of biological cells cannot be reduced to those of its component atoms and molecules, those of plants and animals cannot be reduced to those of its cells, and the mind cannot be reduced to neurons in the brain.

In Part III we give three examples of breaking causal chains - between atoms and molecules, between molecules and cells, and between neurons and the information structures of the mind.

Part IV then makes the case for specific “emergent” properties at those higher hierarchical levels that could not have been predicted from the laws of lower levels. We then defend an emergent capability for “downward causation,” in which biological systems have limited causal powers over their cells, and their cells have causal powers over component atoms and molecules. At the highest level, we show how the mind can exert a supervenient downward causation on the brain. Mental causation is needed for an agent to act willfully. The agent’s actions are adequately determined by the agent’s motives, reasons, feelings, intentions, and desires.

In part V we show that determinism itself is an emergent property. Determinism shows up only when we can average over a large enough number of atoms and molecules so that indeterministic events are statistically insignificant. Since this kind of determinism is only highly probable, and not perfectly certain, we call it “adequate” determinism. We review the process that creates emergent adequately determined macroscopic information structures in the universe, despite the second law of thermodynamics which demands an increase in disorder or entropy.

Part VI situates this quantum physical and informational model of mental causation in the spectrum of theories of mind, somewhere between the classical substance dualism of René Descartes and the mind-body identity theory of Ullin T. Place, Herbert Feigl, and J.J.C Smart.

Part I. An information-based model for non-reductive physicalism.

The leading defender of a non-reductive physicalism was Donald Davidson. Its leading critic is Jaegwon Kim. In his 1970 essay "Mental Events," Davidson described his "Anomalous Monism":

“Mental events such as perceivings, rememberings, decisions, and actions resist capture in the nomological net of physical theory. How can this fact be reconciled with the causal role of mental events in the physical world? Reconciling freedom with causal determinism is a special case of the problem if we suppose that causal determinism entails capture in, and freedom requires escape from, the nomological net. But the broader issue can remain alive even for someone who believes a correct analysis of free action reveals no conflict with determinism. Autonomy (freedom, self-rule) may or may not clash with determinism; anomaly (failure to fall under a law) is, it would seem, another matter.”

In order to allow mental events to cause physical events, yet not be reducible to them, Davidson developed the following set of arguments.

1. "at least some mental events interact causally with physical events"

2. "where there is causality, there must be a law: events related as cause and effect fall under strict deterministic laws."

3. "there are no strict deterministic laws on the basis of which mental events can be predicted and explained." (mental events are "anomalous.")

Davidson viewed his work as extending that of Immanuel Kant on reconciling (eliminating the anomalous contradiction between) freedom and necessity.

Davidson gave the term supervenience a specific philosophical meaning within analytic philosophy. He saw supervenience as the last hope for a non-reductive physicalism, which does not reduce the mental to the physical, the psychological to the neurophysiological.

Davidson set two requirements for supervenience:

1. a domain can be supervenient on another without being reducible to it (non reduction)
2. if a domain supervenes, it must be dependent on and be determined by the subvenient domain (dependence)

In Jaegwon Kim's 1989 presidential address to the American Philosophical Association, he said:

“The fact is that under Davidson's anomalous monism, mentality does no causal work. Remember: in anomalous monism, events are causes only as they instantiate physical laws, and this means that an event's mental properties make no causal difference.”

Kim claims that:

“The most fundamental tenet of physicalism concerns the ontology of the world. It claims that the content of the world is wholly exhausted by matter. Material things are all the things that there are; there is nothing inside the spacetime world that isn't material, and of course there is nothing outside it either. The spacetime world is the whole world, and material things, bits of matter and complex structures made up of bits of matter, are its only inhabitants.”

Kim says that Davidson's goal of "non-reductive physicalism" is simply not possible. The physical world is "causally closed," says Kim:

“what options are there if we set aside the physicalist picture? … This means that one would be embracing an ontology that posits entities other than material substances — that is, immaterial minds, or souls, outside physical space, with immaterial, nonphysical properties.”

An informational theory of mind posits the existence of something physical, yet immaterial. It is both a “non-reductive physicalism” and an “immaterial physicalism.”

The germ of the idea was apparent in a series of papers in the 1950’s and 1960’s by Hilary Putnam and Jerry Fodor, whose theory of functionalism pointed to characteristics of mind that are “multiply realizable” in different physical substrates. They were inspired by the then new digital computers, whose software could be moved between different computers and perform the same functions. Mind is the software in the brain hardware, they argued.

Our informational theory of mind shows how thoughts that are embodied in one mind can be converted from their material instantiation and transformed into the pure energy of sound waves or electromagnetic waves by which they are communicated to other minds, there to be embodied again. During communication, the information in human knowledge is not even embodied in material, though it is still a part of the physical world.

Part II. Quantum physics introduces the chance needed to break the chains of strict causal determinism

The problem of mental causation can be traced back to the first half of the seventeenth century and René Descartes, who divided the world into three distinct substances; God as the primary substance; matter, which has a spatial extension; and mind, a thinking substance which is the locus of intellect and a free will.

Descartes thought that animal and human bodies are machines subject to laws of matter alone. His famous “cogito, ergo sum” argument was used to distinguish his thinking substance from his material body.

“I saw that while I could pretend that I had no body and that there was no world and no place for me to be in, I could not for all that pretend that I did not exist. I saw on the contrary that from the mere fact that I thought of doubting the truth of other things, it followed quite evidently and certainly that I existed; whereas if I had merely ceased thinking, even if everything else I had ever imagined had been true, I should have had no reason to believe that I existed. From this I knew I was a substance whose whole essence or nature is simply to think, and which does not require any place, or depend on any material thing, in order to exist.” (Discourse on Method, 6:32)

Whereas Descartes argued that the thinking substance had freedom of the will, his materialist contemporary Thomas Hobbes saw necessity and deterministic laws of nature that denied human freedom.

“That which I say necessitates and determinates every action is the sum of all those things which, being now existent, conduce and concur to the production of the action hereafter, whereof if any one thing were wanting, the effect could not be produced. This concourse of causes, whereof every one is determined to be such as it is by a like concourse of former causes, may well be called the decree of God.” (Of Liberty and Necessity, § 11)

In the second half of the eighteenth century, the great Isaac Newton discovered his three laws of physics that seemed for many to come down on the side of Hobbes and determinism. Explaining the heavenly motion, Newtonian laws surely could explain all the workings of terrestrial material machines.

The power to predict eclipses of moon and sun many years in advance was extrapolated in the eighteenth-century by Pierre-Simon Laplace to the idea of a super intelligence that can predict the future based on a knowledge of positions, velocities, and forces of all the particles of matter.

Thus arose the concept of “causal closure” and what might be called “the great chain of causation.” But in the late nineteenth century, some philosophers and scientists came to wonder whether our physical laws, derived as they are from fallible experiments and measurements with only finite accuracy, are as absolute and perfect and strict as most scientists and philosophers believed.

Charles Sanders Peirce was the leading philosopher who argued that the world contained absolute chance. Peirce was deeply impressed by chance as a way to bring diversity and "progress" (in the form of increasingly complex organisms) to the world, including the mind. Peirce was unequivocal that chance was a real property of the world. He named it Tyche (τύχη). He writes in his third Monist article, "The Law of Mind,"

“In an article published in The Monist for January, 1891, I endeavored to show what ideas ought to form the warp of a system of philosophy, and particularly emphasized that of absolute chance. In the number of April, 1892, I argued further in favor of that way of thinking, which it will be convenient to christen tychism (from τύχη, chance)... I have begun by showing that tychism must give birth to an evolutionary cosmology, in which all the regularities of nature and of mind are regarded as products of growth.”

Physicist Ludwig Boltzmann was the leading scientist who argued against perfect deterministic laws. Boltzmann's first attempt to derive the second law of thermodynamics (that entropy or disorder in the universe always increases) assumed that gas particles followed strict deterministic dynamical laws, that is, Newton's classical mechanics. But Boltzmann was immediately criticized by his colleagues James Clerk Maxwell and Josef Loschmidt.

Boltzmann's mentor and colleague Loschmidt criticized Boltzmann's demonstration of entropy increase on the grounds that dynamical laws are time reversible. If all the particles could be turned around exactly (or if time could be reversed), in such a case the entropy should decrease, violating the second law.

As a result, Boltzmann developed a statistical version of his H-Theorem, which again showed that entropy would always increase, as long as the fundamental particles themselves had what he called “molecular disorder” or “molecular chaos.”

Boltzmann explained the gas laws of thermodynamics as statistical laws resulting from averaging over an enormous number (billions of billions of billions) of chaotic atoms and molecules. Boltzmann maintained (as his student Franz Exner, and even Exner's student Erwin Schrödinger would briefly insist) that no amount of observational evidence can ever justify our assumptions of strict determinism.[]

Indeed, at the beginning of the twentieth century, observational evidence led to the notion that fundamental physical quantities like energy and momentum need to be “quantized,” putting irreducible limits on our ability to observe atoms and molecules. This in turn led to quantum indeterminism, breaking the causal chain of determinism that was thought to put limits on the workings of the human mind.

Max Planck in 1900 introduced the quantum concept. He explained the spectral distribution of colors (wavelengths) in electromagnetic radiation by using Boltzmann’s principle that the entropy S of a gas is related to the probabilities W for random distribution of molecules in different places in its container (S = klogW, where k is Boltzmann’s constant). Boltzmann’s calculations of probabilities used the number of ways that particles can be distributed in various volumes of space. Planck used the same combinatorial analysis, but now for the number of ways that elements of energy could be distributed among a number of electromagnetic oscillators. To simplify the calculations, both Boltzmann and Planck assumed that energies could be multiples of a unit of energy, E = ε, 2ε, 3ε …. Plank regarded this quantum hypothesis as a mathematically convenient device. He did not think it represented reality. Nevertheless, this was the beginning of quantum theory. And even more importantly it provided the first connection between the laws of matter and the laws of pure energy (radiation). Planck told his son he had discovered something as significant as Copernicus or Newton. [ref- Kuhn]