Mental causation is a specific case of the more general problem of downward causation, for example the downward control of the motions of a cell's atoms and molecules by supervening biological macromolecules. Is the molecular biology of a cell reducible to the laws governing the motions of its component molecules, or are there emergent laws governing motions at the cellular level, the organ level, the organism level, and so on up to the mental level?

Can emergent properties or laws at the higher levels of a physical-chemical-based biological system prevent those higher levels from being reduced to the properties and laws of the base physical level?

The idea of something like downward causation was implicit in the work of "emergentists" like John Stuart Mill, George Henry Lewes, C. Lloyd Morgan, Samuel Alexander, and C. D. Broad

Although Mill did not use the term "emergent," he made the concept clear enough:

The chemical combination of two substances produces, as is well known, a third substance with properties different from those of either of the two substances separately, or of both of them taken together. Not a trace of the properties of hydrogen or of oxygen is observable in those of their compound, water.

(A System of Logic, Book III, chapter VI)

Lewes coined the term "emergent" in 1875:

Although each effect is the resultant of its components, the product of its factors, we cannot always trace the steps of the process, so as to see in the product the mode of operation of each factor. In the latter case, I propose to call the effect an emergent. It arises out of the combined agencies, but in a form which does not display the agents in action.

(Problems of Life and Mind,(1875), vol. 2, p. 412)

In his 1920 book Space, Time, and Deity Samuel Alexander cited Lloyd Morgan as the source of emergentism, and wrote:

Mind is, according to our interpretation of the facts, an 'emergent' from life, and life an emergent from a lower physico-chemical level of existence.

(Space, Time, and Deity (1920), vol. 2, p. 14)

Later, in his 1922 Gifford Lectures and 1923 book Emergent Evolution, Lloyd Morgan defined emergent evolution and introduced the related "top-down" concept of hierarchical supervenience:

...in the physical world emergence is no less exemplified in the advent of each new kind of atom, and of each new kind of molecule. It is beyond the wit of man to number the instances of emergence. But if nothing new emerge - if there be only regrouping of pre-existing events and nothing more - then there is no emergent evolution.

Under emergent evolution there is progressive development of stuff which becomes new stuff in virtue of the higher status to which it has become raised under some supervenient kind of substantial gotogetherness.

(Emergent Evolution (1923), pp. 1-6)

Brian McLaughlin dubbed these thinkers the "British Emergentists." He developed an "idealized" version of British Emergentism and synthesisized what most of these thinkers had in common into a coherent and representative picture. He says:

British Emergentism maintains that everything is made of matter: There are, for example, no Cartesian souls, or entelechies, vital elan, or the like. And it holds that matter is grainy, rather than continuous; indeed, that it bottoms-out into elementary material particles, atoms or more fundamental particles...Moreover, on its view, nothing happens, no change occurs, without some motion of elementary particles. And all motion is to the beat of the laws of mechanics.

According to British Emergentism, there is a hierarchy of levels of organizational complexity of material particles that includes, in ascending order, the strictly physical, the chemical, the biological, and the psychological level. There are certain kinds of material substances specific to each level. And the kinds of each level are wholly composed of kinds of lower levels, ultimately of kinds of elementary material particles. Moreover, there are certain properties specific to the kinds of substances of a given level. These are the "special properties" of matter...

What is especially striking about British Emergentism, however, is its view about the causal structure of reality. I turn to that view in the following two paragraphs.

British Emergentism maintains that some special science kinds from each special science can be wholly composed of types of structures of material particles that endow the kinds in question with fundamental causal powers. Subtleties aside, the powers in question "emerge" from the types of structures in question...

Now, the exercise of the causal powers in question will involve the production of movements of various kinds. Indeed, Emergentism maintains that special kinds, in virtue of possessing certain types of minute internal structures, have the power to influence motion. And here is the striking point: They endow the kinds with the power to influence motion in ways unanticipated by laws governing less complex kinds and conditions concerning the arrangements of particles. Emergentism is committed to the nomological possibility of what has been called "downward causation".

Vitalists like Henri Bergson and Hans Driesch also implicitly supported the idea of emergent or non-physical causes, without which they thought that life and mind could not have emerged from physical matter, and without which mind could not be a causal force in the world.

Holistic critics attacked this view as reducing the mind to the brain, leaving the mind merely an epiphenomenon or illusion. This fit well into the reductionist program of the logical empiricists of the Vienna Circle, who promoted the idea of the Unity of Science. All events should be reducible to physical events, and in particular, all explanations should be traceable to causes originating in the physical material components of the universe.

The first philosophers to argue for an identity of mind (or consciousness) and brain include Ullin T. Place (1956), Herbert Feigl, and J.J.C.Smart (1959).

Place explicitly describes "consciousness as a brain process," specifically as "patterns" of brain activity. He does not trivialize this identity as a succession of individual "mental events and physical events" in some kind of causal chain. He compares this identity to the idea that "lightning is a motion of electrical charges."

("Is Consciousness a Brain Process?", in British Journal of Psychology, 47, pp.44-50 (1956))

Herbert Feigl's work was independent of Place's, but he said that the fundamental idea had been held by many earlier materialist (monist) thinkers. He thought it was stated clearly by Vienna Circle philosopher Rudolf Carnap in 1925. Feigl describes his own thesis:

The identity thesis which I wish to clarify and to defend asserts that the states of direct experience which conscious beings "live through" and those which we confidently ascribe to some of the higher animals, are identical with certain (presumably configurational) aspects of the neural processes in these organisms.

("The 'Mental' and the 'Physical'", in Concepts, Theories, and the Mind-Body Problem, University of Minnesota Press (1958), p.150)

J.J.C.Smart clarified and extended the identity theory of his colleague U.T.Place

When I say that a sensation is a brain process or that lightning is an electric discharge, I am using "is" in the sense of strict identity. (Just as in the — in this case necessary — proposition "7 is identical with the smallest prime number greater than 5.") When I say that a sensation is a brain process or that lightning is an electric dis- charge I do not mean just that the sensation is somehow spatially or temporally continuous with the brain process or that the lightning is just spatially or temporally continuous with the discharge.

("Sensations and Brain Processes", in Philosophical Review 68 pp. 141-156 (1959))

Smart is a strong materialist. He says "A man is a vast arrangement of physical particles, but there are not, over and above this, sensations or states of consciousness." (ibid.) Compare Anthony Cashmore, who says we are "just a bag of chemicals."

In the 1960's the neuroscientist Roger Sperry claimed that higher levels in a hierarchy could act causally on the base level. He cited a wheel rolling downhill as an example of what he called "downward causal control." The atoms and molecules are caught up and overpowered by the higher properties of the whole. Sperry compared the rolling wheel to an ongoing brain process or a progressing train of thought in which the overall properties of the brain process, as a coherent organizational entity, determine the timing and spacing of the firing patterns within its neural infrastructure. A few years later (1974), Donald Campbell coined the phrase "downward causation."

The locus classicus of recent discussions of mental causation is Donald Davidson's 1970 essay "Mental Events," which was revisited in his 1993 essay, "Thinking Causes," published together with 15 critical essays on Davidson's work in the 1993 book Mental Causation, edited by John Heil and Alfred Mele.

Davidson claimed three things:

1. That mental events are causally related to physical events
2. That causal relations are normally backed by strict (deterministic) laws
3. But that there are no such strict laws for mental events acting on physical events

Davidson's goal is to deny the reducibility of mental events to physical events in the lower levels, even to deny the physicist's claim that the motions of the atoms and molecules at the lowest level are causally determinative of everything that happens at higher levels.

what options are there if we set aside the physicalist picture? Leaving physicalism behind is to abandon ontological physicalism, the view that bits of matter and their aggregates in space-time exhaust the contents of the world. 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.

(Physicalism, or Something Near Enough, p. 71)

Kim diagrams Davidson's view of mental events supervening on physical events, to illustrate his claim that having both mental and physical causes would be "overdetermination" and thus one is redundant and must be excluded.

This view of the physical and biological world as made up of isolatable and discrete events is too simplistic. A physical "event" is subjectively singled out by a human observer from a practically infinite number of objective physical events at the atomic and molecular level. Its "cause" is arbitrarily abstracted from complex processes with enormous numbers of possible causes. A mental event is embedded in a biological system beyond "astronomical" complexity.

Recap of the Problem of Mental Causation according to Kim.

While the original mind-body problem was simply the puzzle of how an immaterial mind could cause a material body to move, lately the problem of mental causation has been recast as the logical resolution of one basic premise and a conclusion, which we might call the standard argument against mental causation:

1. The only causes are physical causes. (These causes need not be deterministic. An indeterministic quantum statistical event gives us the probabilities for subsequent events, "causing" them in a way that is not pre-determined.)
2. Therefore, mental events cannot cause physical events.

The Emergence of Life from Matter and Mind from Life.

According to British Emergentism, there is a hierarchy of levels of organizational complexity of material particles that includes, in ascending order, the strictly physical, the chemical, the biological, and the psychological level. As we have seen, upper hierarchical levels have the power to influence motion in ways unanticipated by laws governing less complex kinds and conditions concerning the arrangements of particles. Emergentism is committed to the nomological possibility of what has been called "downward causation," control by an upper level of the component particles of the lower levels. We can now demonstrate that the Emergentists' hypothesis is actually realized in biological systems.

The informational analysis of non-reductive physicalism must show exactly how information does not move in the upward direction between hierarchical levels (fundamentally because noise in the lower level makes motions incoherent), but that information does move down as the higher-level information-processing system uses it to manipulate individual physical particles (maintaining a high signal-to-noise ratio in the upper level), as the British empiricists imagined.

Quantum Randomness Blocks "Bottom-Up" Causation,
Information-Processing Structures Enable Downward Causation

We shall now see that quantum and thermal noise breaks any upwardly causal deterministic chains between the physics of the atomic and molecular level and the biophysics of the organic world. It also breaks any upward deterministic chains between the neurobiological brain and the mind, replacing them with a statistical causality that provides us with what William James called “some looseness in the joints.”

We present two processes that exhibit randomness in the component atoms and molecules, thus blocking any organized upward influences. The first is present in every biological cell. The other is critically important in the operation of neurons. The first separates the living from the simply material. The latter is at the mind/brain boundary.

Ribosomes Build Hemoglobin from Randomly Moving Amino Acids (Life from Matter)

The twenty amino acids move about randomly in a cell, the consequence of thermal and quantum noise. Attached to them are tiny bits of transfer RNA, each with three letters of the genetic code that identify them. They bump randomly into the ribosome, which may be moving along a sequence of the genetic code written in messenger RNA sent from the cell nucleus, which has noticed that more of a specific protein or enzyme is needed. This random motion shows us that no organized or coherent information is present in the unattached tRNAs that could cause something from the bottom up to emerge at a higher level.

[Look at the animation of mRNA translation] Notice the absurdity of the idea that the random motions of the transfer RNA molecules (green in the video at right), each holding a single amino acid (red), are carrying pre-determined information of where they belong in the protein.

It is the information processing of the higher-level ribosome that is in control. As the ribosome moves along the string of mRNA, it reads the next three-letter codon and waits for a tRNA with the matching anti-codon to collide randomly. With over 60 codons for the 20 amino acids, it might be some time before the desired amino acid shows up. Note that it is the high speed of random motions that allows this process to proceed rapidly. Consider the case of hemoglobin.

When a ribosome assembles 330 amino acids in four symmetric polypeptide chains (globins), each globin traps an iron atom in a heme group at the center to form the hemoglobin protein. This is downward causal control of the amino acids, the heme groups, and the iron atoms by the ribosome. The ribosome is an example of Erwin Schrödinger's emergent "order out of order," life "feeding on the negative entropy" of digested food.

When 200 million of the 25 trillion red blood cells in the human body die each second, 100 million new hemoglobins must be assembled in each of 200 million new blood cells . With the order of a few thousand bytes of information in each hemoglobin, this is 10 thousand x 100 million x 200 million =
2 x 10²⁰ bits of information per second, a million times more information processing than today's fastest computer CPU.

The ribosome is an information-processing biological system that has emerged from the lower level of chemistry and physics to exert downward causation on the atomic and molecular components needed to manufacture hemoglobin.

Ion Pumps in Neurons Organize Randomly Moving Individual Atoms (Mind from Life)

When a single neuron fires, the active potential rapidly changes the concentration of sodium (Na+) ions inside the cell and potassium (K+) ions outside the cell. Within milliseconds, thousands of sodium-potassium ion transporters in the thin lipid bilayer of the cell wall must move billions of those ions, two or three at a time between inside and outside the cell wall, to get the neuron ready to fire again.

All the individual ions, atoms, and molecules in the cell are moving rapidly in random directions. The indeterministic motions of the ions randomly move some near the pump opening, where quantum collaborative forces can capture them in a lock-and-key structure. The idea that the physical/chemical base level contains enough information in the motion of its atoms and molecules to cause and completely explain the operations of the higher levels of life and mind is simply absurd.

The emergent biological machinery of a sodium-potassium pump exerts downward causation on the ions, powered by ATP energy carriers (feeding on negative entropy).

The sodium-potassium pump in our neurons is as close to a Maxwell's Demon as anything we are ever likely to see.

When many motor neurons fire, innnervating excitatory post-synaptic potentials (EPSPs) that travel down through the thalamus and the spinal cord where they cause muscles to contract, that is as literal as downward causation gets between the mind and the body. When the emergent mind decides to move the body, mental causation is realized as downward causation.

The Information Solution to the Problem of Mental Causation.

Information philosophy understands mental events as immaterial thoughts, which are normally only unrealized possibilities for action. Thoughts are embodied in the neural information structures of the brain, where they are stored along with memories of past experience. As such, they are physical and are temporarily even material, in some sense.

But when they are transferred (communicated) to other parts of the brain, out to other minds, or for storage in the external environment, thoughts are converted from a material substrate to various forms of energy. Temporarily, they are quite non-material, as philosophers for centuries have imagined thoughts in an immaterial mind might be. Once stored, they are again embodied in matter.

Of course, thoughts or ideas can be unpredictably altered before storage, by noise in the communication. They can also be altered randomly by irreducibly indeterministic errors in the retrieval of the information. Here lies the basis for creative mistakes, to be evaluated by a process of intelligent selection. (As Augustine noted, the Latin intelligere means "to select.")

The information solution to the mind-body problem can be interpreted as providing a non-reductive physical interpretation of mind. This model of mind supervenes on the neural brain structures that embody the information (while it is being stored). But the intellectual content of the information is not the resultant of whatever physical processes are coming from lower layers in a hierarchical structure. The physical brain is a plastic storage medium adequately determined to store the information content of these immaterial thoughts, and normally to store it accurately.

With reference to popular (if flawed) computational theories of mind, we note that the "software" contents of a computer program, as well as the execution of the program, is in no way determined or "caused" by the computer "hardware." Similarly, ideas are not determined by the ink on a printed page or the pixels on a computer screen, but by the human minds that put them there.

"Bottom-up" Physical Processes Are Not Deterministic

When small numbers of atoms and molecules interact, their motions and behaviors are indeterministic, governed by the rules of quantum mechanics.

Note that this is the reverse of the normal view that microscopic processes are time reversible and deterministic, where macroscopic processes for unaggregated gas particles are statistical and irreversible.

However, when large numbers of microscopic particle get together in chemically or gravitationally bound aggregates, the indeterminacy of the individual particles gets averaged over and macroscopic adequately deterministic laws "emerge."

Determinism is an emergent property that shows up in the macroscopic world.

The "laws of nature," such as Newton's laws of motion, are all statistical laws, however close they appear to being certain. They "emerge" when large numbers of atoms or molecules get together. For large enough numbers, the probabilistic laws of nature approach practical certainty. But the fundamental indeterminism of component atoms never completely disappears.

It therefore follows that physical brain events are not pre-determined by the events in lower hierarchical levels, not events in the base physical level, nor even in the biological level.

And the world is not "causally closed" by deterministic physical laws of nature, as assumed by so many philosophers (e.g., Feigl, Smart, Kim).

Moreover, since some "mental events" are large enough information structures to be adequately determined, these mental events can act causally on lower biological and physical levels in the hierarchy, in particular, the mind can move the body and all its contained physical particles, thus solving the mind-body problem.

A specific example of the mind causing an action, while not itself being caused by antecedent events is the following. Faced with a decision of what to do next, the mind considers several possible alternatives, at least some of which are creatively invented based on random ideas that just "come to mind." Other possible alternatives might be familiar options, even habits, that have frequently been done in earlier similar situations.

All these alternatives show up as "neural correlates" - brain neurons firing. When the alternatives are evaluated and one is selected, the selected action results in still other neurons firing, some of which connect to the motor cortex that signals muscles to move the body.

Apart from the occasional indeterministic generation of creative new alternative ideas, this whole causal process is adequately determined and it is downwardly causal. Mental events are causing physical body events.

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Quantum Physics and the Problem of Mental Causation". Presented June 6, 2013 at a conference in Milan on "Quantum Physics Meets the Philosophy of Mind".