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Philosophers

Mortimer Adler
Rogers Albritton
Alexander of Aphrodisias
Samuel Alexander
William Alston
Anaximander
G.E.M.Anscombe
Anselm
Louise Antony
Thomas Aquinas
Aristotle
David Armstrong
Harald Atmanspacher
Robert Audi
Augustine
J.L.Austin
A.J.Ayer
Alexander Bain
Mark Balaguer
Jeffrey Barrett
William Belsham
Henri Bergson
George Berkeley
Isaiah Berlin
Richard J. Bernstein
Bernard Berofsky
Robert Bishop
Max Black
Susanne Bobzien
Emil du Bois-Reymond
Hilary Bok
Laurence BonJour
George Boole
Émile Boutroux
F.H.Bradley
C.D.Broad
Michael Burke
C.A.Campbell
Joseph Keim Campbell
Rudolf Carnap
Carneades
Ernst Cassirer
David Chalmers
Roderick Chisholm
Chrysippus
Cicero
Randolph Clarke
Samuel Clarke
Anthony Collins
Antonella Corradini
Diodorus Cronus
Jonathan Dancy
Donald Davidson
Mario De Caro
Democritus
Daniel Dennett
Jacques Derrida
René Descartes
Richard Double
Fred Dretske
John Dupré
John Earman
Laura Waddell Ekstrom
Epictetus
Epicurus
Herbert Feigl
John Martin Fischer
Owen Flanagan
Luciano Floridi
Philippa Foot
Alfred Fouilleé
Harry Frankfurt
Richard L. Franklin
Michael Frede
Gottlob Frege
Peter Geach
Edmund Gettier
Carl Ginet
Alvin Goldman
Gorgias
Nicholas St. John Green
H.Paul Grice
Ian Hacking
Ishtiyaque Haji
Stuart Hampshire
W.F.R.Hardie
Sam Harris
William Hasker
R.M.Hare
Georg W.F. Hegel
Martin Heidegger
Heraclitus
R.E.Hobart
Thomas Hobbes
David Hodgson
Shadsworth Hodgson
Baron d'Holbach
Ted Honderich
Pamela Huby
David Hume
Ferenc Huoranszki
William James
Lord Kames
Robert Kane
Immanuel Kant
Tomis Kapitan
Jaegwon Kim
William King
Hilary Kornblith
Christine Korsgaard
Saul Kripke
Andrea Lavazza
Keith Lehrer
Gottfried Leibniz
Leucippus
Michael Levin
George Henry Lewes
C.I.Lewis
David Lewis
Peter Lipton
C. Lloyd Morgan
John Locke
Michael Lockwood
E. Jonathan Lowe
John R. Lucas
Lucretius
Alasdair MacIntyre
Ruth Barcan Marcus
James Martineau
Storrs McCall
Hugh McCann
Colin McGinn
Michael McKenna
Brian McLaughlin
John McTaggart
Paul E. Meehl
Uwe Meixner
Alfred Mele
Trenton Merricks
John Stuart Mill
Dickinson Miller
G.E.Moore
Thomas Nagel
Friedrich Nietzsche
John Norton
P.H.Nowell-Smith
Robert Nozick
William of Ockham
Timothy O'Connor
Parmenides
David F. Pears
Charles Sanders Peirce
Derk Pereboom
Steven Pinker
Plato
Karl Popper
Porphyry
Huw Price
H.A.Prichard
Protagoras
Hilary Putnam
Willard van Orman Quine
Frank Ramsey
Ayn Rand
Michael Rea
Thomas Reid
Charles Renouvier
Nicholas Rescher
C.W.Rietdijk
Richard Rorty
Josiah Royce
Bertrand Russell
Paul Russell
Gilbert Ryle
Jean-Paul Sartre
Kenneth Sayre
T.M.Scanlon
Moritz Schlick
Arthur Schopenhauer
John Searle
Wilfrid Sellars
Alan Sidelle
Ted Sider
Henry Sidgwick
Walter Sinnott-Armstrong
J.J.C.Smart
Saul Smilansky
Michael Smith
Baruch Spinoza
L. Susan Stebbing
Isabelle Stengers
George F. Stout
Galen Strawson
Peter Strawson
Eleonore Stump
Francisco Suárez
Richard Taylor
Kevin Timpe
Mark Twain
Peter Unger
Peter van Inwagen
Manuel Vargas
John Venn
Kadri Vihvelin
Voltaire
G.H. von Wright
David Foster Wallace
R. Jay Wallace
W.G.Ward
Ted Warfield
Roy Weatherford
William Whewell
Alfred North Whitehead
David Widerker
David Wiggins
Bernard Williams
Timothy Williamson
Ludwig Wittgenstein
Susan Wolf

Scientists

Michael Arbib
Bernard Baars
Gregory Bateson
John S. Bell
Charles Bennett
Ludwig von Bertalanffy
Susan Blackmore
Margaret Boden
David Bohm
Niels Bohr
Ludwig Boltzmann
Emile Borel
Max Born
Satyendra Nath Bose
Walther Bothe
Hans Briegel
Leon Brillouin
Stephen Brush
Henry Thomas Buckle
S. H. Burbury
Donald Campbell
Anthony Cashmore
Eric Chaisson
Jean-Pierre Changeux
Arthur Holly Compton
John Conway
John Cramer
E. P. Culverwell
Charles Darwin
Terrence Deacon
Louis de Broglie
Max Delbrück
Abraham de Moivre
Paul Dirac
Hans Driesch
John Eccles
Arthur Stanley Eddington
Paul Ehrenfest
Albert Einstein
Hugh Everett, III
Franz Exner
Richard Feynman
R. A. Fisher
Joseph Fourier
Lila Gatlin
Michael Gazzaniga
GianCarlo Ghirardi
J. Willard Gibbs
Nicolas Gisin
Paul Glimcher
Thomas Gold
A.O.Gomes
Brian Goodwin
Joshua Greene
Jacques Hadamard
Patrick Haggard
Stuart Hameroff
Augustin Hamon
Sam Harris
Hyman Hartman
John-Dylan Haynes
Martin Heisenberg
Werner Heisenberg
John Herschel
Jesper Hoffmeyer
E. T. Jaynes
William Stanley Jevons
Roman Jakobson
Pascual Jordan
Ruth E. Kastner
Stuart Kauffman
Simon Kochen
Stephen Kosslyn
Ladislav Kovàč
Rolf Landauer
Alfred Landé
Pierre-Simon Laplace
David Layzer
Benjamin Libet
Seth Lloyd
Hendrik Lorentz
Josef Loschmidt
Ernst Mach
Donald MacKay
Henry Margenau
James Clerk Maxwell
Ernst Mayr
Ulrich Mohrhoff
Jacques Monod
Emmy Noether
Howard Pattee
Wolfgang Pauli
Massimo Pauri
Roger Penrose
Steven Pinker
Colin Pittendrigh
Max Planck
Susan Pockett
Henri Poincaré
Daniel Pollen
Ilya Prigogine
Hans Primas
Adolphe Quételet
Juan Roederer
Jerome Rothstein
David Ruelle
Erwin Schrödinger
Aaron Schurger
Claude Shannon
David Shiang
Herbert Simon
Dean Keith Simonton
B. F. Skinner
Roger Sperry
Henry Stapp
Tom Stonier
Antoine Suarez
Leo Szilard
William Thomson (Kelvin)
Peter Tse
Heinz von Foerster
John von Neumann
John B. Watson
Daniel Wegner
Steven Weinberg
Paul A. Weiss
John Wheeler
Wilhelm Wien
Norbert Wiener
Eugene Wigner
E. O. Wilson
H. Dieter Zeh
Ernst Zermelo
Wojciech Zurek

Presentations

Biosemiotics
Free Will
Mental Causation
James Symposium
 
John Carew Eccles

Few scientists have had more insight into the physical workings of the mind than the great neurobiologist John Eccles. His partnership with Karl Popper produced years of conversation about the interaction between a non-material mind and the material brain. He and Popper were both dualists. His "philosophical position was diametrically opposite to those who would relegate conscious experience to a mere epiphenomenon." (Eccles, Facing Reality, 1970, p.1.)
Conversations with Popper sometimes denied any role for quantum uncertainty. That would only be chance, which could not provide moral responsibility for human actions. But Popper did produce a two-stage model for free will in 1965, under the influence of Arthur Holly Compton. Eccles wrote and lectured frequently on free will. We provide an excerpt from Facing Reality on Free Will and Creativity. There is no sign here of Popper's idea, nor of Eccles' radical hypothesis that mind used the immaterial probability wave function, based on an observation of Henry Margenau.
In this selection, Eccles has reworked the 1952 conclusion of his Waynflete lectures at Oxford - The Neurophysiological Basis of Mind, Oxford, 1953, pp.271-286.

Facing Reality, 1970, pp.118-129

From Chapter VIII, Man, Freedom, and Creativity.
1. Free Will

The self has other properties besides purely being able to experience things as described in Chapters IV and V. It can also do things. And so we are confronted with the problem of free-will. We can argue: do we have free-will, or are all our decisions the manifestations of something that is in-born, plus all our training or conditioning? If a statement is made: "I do not have free-will," two inferences can be made: this statement could be a result of a conditioning, the subject being well-trained to repeat it like a parrot, which makes it devoid of significance; or the subject may claim that he has free-will just to make this statement, which is an arbitrary and self-stultifying statement.

Whatever their expressed beliefs, people in fact behave as if they have free-will, which, I think, is best shown by trivial things in life—whether, for example, I can take a coin and put it here or there, turn it over or do the most capricious things with it. We demand of our nervous and muscular equipment that we can at will cause it to carry out any desired actions which are within our power, no matter how trivial or capricious. Remarkable observations can be made by evoking movements by stimulating the motor areas of the brain in a conscious subject. Though these movements were elicited as normally by messages from the motor cortex, the subject distinguishes quite clearly between them and those that he voluntarily initiated. He will say, "This movement is due to something done to me and not something done by me."

There is no answer to such a question as: Is any reconciliation possible between the direct experience that an act of will can call forth a muscular movement, and on the other hand, the scientific account whereby such a muscular movement results from an activity of nerve cells in the brain, which in turn is relayed by nerve impulses eventually to muscles? It is my contention that these questions concerning the problem of brain-mind liaison have been wrongly posed.

I have a direct experience that my thought can lead to action. I can decide on a particular action, perhaps of the most trivial nature, and my muscular movements can be directed towards accomplishing that act. I have no experience of the manner in which my willing leads to action. Naturally, scientific investigation can be applied to study the sequence of events leading to movement: the discharges of pyramidal neurones of the motor cortex; the propagation of these impulses down the pyramidal tract; the discharge of impulses so evoked from motoneurones and propagation out to muscles leading to the muscular activation and eventual contraction. There would be no evidence supporting my belief that my body does carry out my willed movements. However there is an evident inadequacy in this documentation. As yet we have no knowledge about the neuronal pathways upstream from the pyramidal cells of the motor cortex (PHILLIPS, 1966). Presumably there are complex patterns of neuronal activity converging onto the motor cortex, and these would be of immense complexity as followed upstream.

A remarkable example of extremely fine voluntary control has been described by BASMAJIAN (1963). The rhythmic discharges of a single motoneurone can be visualized by a subject, being led off by an electrode in one of his muscles and displayed after amplification on a cathode ray screen and by a loudspeaker. After a training period of some hours he is able to vary the frequency of discharge of that single cell at will and to cause it to discharge in preference to other nerve cells to that muscle, and he even can do this in the absence of the visual or auditory aids. These experiments provide remarkable examples of the skill and finesse of the voluntary control of movement.

Curiously enough, the most compelling evidence for the belief in free-will comes when there is some failure in the control of movement. If I find that I cannot direct my muscular movements in some willed manner, as, for example, taking a coin and putting it on some particular square of a chess-board, I would immediately recognize this as due to some disorder in my nervous system, which is called compulsion neurosis. I would consult a neurologist or a psychiatrist; and this would be the reaction of all normal human beings in a civilized society. Thus the belief that it is possible to exert a conscious control of movement is best demonstrated by the response to any untoward limitation of this so-called "freedom of the will."

It is not contended that all action is willed. There is no doubt that a great part of the skilled activity devolving from the cerebral cortex is stereotyped and automatic, as for example the routine driving of a car, and may be likened to the control of breathing by the respiratory centers. But it is contended that it is possible voluntarily to assume control of such actions, even of the most trivial kind, just as we may within limits exercise a voluntary control over our breathing.

The principal grounds for the theoretical belief that this control is an illusion are derived from the assumptions that both physics and neurophysiology give a deterministic explanation of all events in the brain and that we are entirely within this deterministic scheme. In this context reference may be made to the discussion by POPPER (1950) in which he concludes that not only quantum physics but even "classical mechanics is not deterministic, but must admit the existence of unpredictable events." A similar argument has been developed by MACKAY (1966). The neurophysiology of a deterministic character is merely a primitive reflexology, and not related at all to the dynamic properties of the immense neuronal complexities of the brain. There are thus no sound scientific grounds for denying the freedom of the will, which, ironically, must be assumed if we are to act as scientific investigators.

One can surmise from the extreme complexity and refinement of its organization that there must be an unimagined richness of properties in the active cerebral cortex. Meanwhile, I continue to believe in the freedom of my will, though its mode of operation cannot at present be explained scientifically; nevertheless it is important to speculate in order to develop ideas about possible or conceivable physiological mechanisms.

The Neurophysiological Problem of Will

An important neurophysiological problem arises as soon as we attempt to consider in detail the events that would occur in the cerebral cortex when, by exercise of "will," some change is induced in the response to a given situation. As argued above, in a situation where "will" is operative, there will be a changed pattern of discharge down the pyramidal tract and this change must be brought about because there is a change in the spatio-temporal pattern of influences playing upon the pyramidal cells in the motor cortex. If the "will" really can modify our reactions in a given situation, we have somewhere in the complex patterned behaviour of the cortex to find that the spatiotemporal pattern which is evolving in that given situation is modified or deflected into some different pattern.

Quantitative Aspect of Spread of Activity in Neuronal Networks

In the formulation of problems concerning activity in neuronal network: it is of value to have a model of the simplest possible network (Fig. 28 A cf. BURNS, 1951, Fig. 10). Each neurone is assumed to have only two excitatory synaptic knobs on its surface and its axon has only two excitatory knobs on two other neurones. Further it is assumed that the synaptic connexions so formed are of a two-dimensional pattern that allows the neurones to be arranged schematically in the rectangular net-like form of Fig. 28A, where it will be noticed that there is virtual radial symmetry from any point and the possibility of indefinite extension in every direction.

schematic model

If each neurone receives and gives three synaptic contacts, a similar construction with radial symmetry is possible in three-dimensional network (Fig. 28 B). As shown in Fig. 28 these constructions would give alternating direction of transmission in the successive lines in any plane. Similarly, if each neurone gave and received n synapses, the pattern could be accommodated to an n-dimensional network. The problem of the mode of action of the will can be simplified and sharpened by considering firstly the behavior of a single neurone in the active neuronal network of the cortex. Suppose some small "influence" were exerted at a node that would make a neurone discharge an impulse at a level of synaptic excitation which would otherwise have been just ineffective, that is, in general to raise the probability of its discharge. Such a discharged impulse would in turn have an excitatory effect on all the other nodes on which it impinges, raising the probability of their discharge, and so on. If we assume, as above, that the transmission time from node to node occupies 1 msec, then, even on the two-dimensional net of Fig. 28 A, a spread to a large number of neurones is possible in, say, 20 msec, a time that is chosen because it is at the lower limit of duration of discrete mental events.

In order to frame a precise problem, we can firstly consider the schematic neuronal networks of Fig. 28 which are assumed to be cortical neurones — both the pyramidal cells and the very numerous stellate cells. We make the postulates that at zero time a neurone (for example X in Fig. 28 A) is caused to discharge an impulse into the quiescent network and that activation of one synapse is adequate to cause any neurone to discharge an impulse. For the network of Fig. 28 A. the total number of neurones, N, caused to discharge impulses is given by the formula (SAWYER, 1951):

N = 2m2 — 2m + 2

where m is the number of nodes traversed. In 20 msec m=20, the internodal time being assumed as 1 msec; hence the number of neurones activated is 762.

On the same assumptions, but with a multi-dimensional network constructed according to the conventions of Fig. 28, the number of activated neurones, N, is given, where m is large relative to n, by the general formula (SAWYER, 1951):

N ≈ (2n/n!) m2

when m = 20 (i. e. within 20 msec) and with n = 3 (Fig. 28 B), N is of the order 104. With n = 4 and 5 respectively, N is of the order 105 and 8 x 105.

These calculations are intended merely to give some indication of the large number of cortical neurones that could be affected by a discharge originating in any one. In order to apply them to our problem of how "will" could act on the cerebral cortex, it is necessary to take into account the evidence that "will" can act on the cortical neuronal network only when a considerable part of it is at a relatively high level of excitation, i.e. we have to assume that, for "will" to be operative, large population, of cortical neurones are subjected to strong synaptic bombardment, and are stimulated thereby to discharge impulses which bombard other neurones. Under such dynamic conditions it may be conservatively estimated that, out of the hundred or more synaptic contacts made by any one neurone, at least four or five would be critically effective (when summed with synaptic bombardments by other neurones) in evoking the discharge of neurones next in series. The remainder would be ineffective because the recipient neurones would not be poised at this critical level of excitability, being either at a too low level of excitation, or at a too high level, so that the neuronal discharge occurs regardless of this additional synaptic bombardment. Thus at any instant the postulated action of the "will" on any one neurone would be effectively detected by the "critically poised neurones" on which it acts synaptically.

So long as the assumed number of critically effective synaptic excitatory actions by each neurone is kept at the low levels used in the above calculations, it is probable that the conventions of the network structures of Fig. 28 give an approximate method of allowing for all the mass of feed-back connections that occur in the closed-chain linkages of the cerebral cortex (LORENTE DE NO, 1933, 1934, 1943). Further, since the cortex is approximately 3 mm thick and the mean density of neurones 40,000 per sq. mm of surface (THOMPSON, 1899), the spread to some hundreds of thousands of neurones can be treated as spreading indefinitely in all directions without serious restriction by the sheet-like structure of the cortex. Hence we may conclude that, when a region of the cortical neuronal network is at a high level of activity, the discharge of an impulse by any one neurone will have contributed directly and indirectly to the excitation of hundreds of thousands of other neurones within the very brief time of 20 msec.

A Neurophysiological Hypothesis of Will

As a restatement of the conclusion of the preceding section we may say that in the active cerebral cortex within 20 msec the pattern of discharge of even hundreds of thousands of neurones would be modified as a result of an "influence " that initially caused the discharge of merely one neurone. But further, if we assume that this "influence" is exerted not only at one node of the active network, but also over the whole field of nodes in some sort of spatio-temporal patterning, then it will be evident that potentially the network is capable of integrating the whole aggregate of "influences" to bring about some modification of its patterned activity, that otherwise would be determined by the pattern of afferent input and its own inherent structural and functional properties. Such integration would occur over hundreds of thousands of nodes in a few milliseconds, the effects exerted on any and every node being correlated in the resultant patterned activity of the surrounding hundreds of thousands of neurones. Thus in general. the spatio-temporal pattern of activity would be determined not only by (i) the micro-structure of the neural net and its functional properties as built up by genetic and conditioning factors and (ii) the afferent input over the period of short-term memory, but also (iii) by the postulated "field of mind influence." For example, in Fig. 29 the spatio-temporal pattern determined by factors (i) and (ii) is shown diagrammatically by the shaded structure bounded by the continuous line, while a possible modification by factor (iii) is indicated by the paths outlined by broken lines at B and C. Fig. 29 can be considered as showing boundaries of multilane neuronal traffic as indicated in Figs. 10 and 12.

schematic model

It can be claimed that no physical instrument would bear comparison with the postulated performance of the active cerebral cortex as a detector of minute "fields of influence" spread over a microscopic pattern am with temporal sequences of milliseconds. The integration, within a few milliseconds, of "influences" picked up at hundreds of thousands of nodes would be unique, particularly when it is remembered that the integration is no mere addition, but is exerted to modify in some specific way "a shifting harmony of sub-patterns" of neuronal activity, achieving expression through the modifications so produced.

Thus, the neurophysiological hypothesis is that the "will" modifies the spatiotemporal activity of the neuronal network by exerting spatiotemporal "fields of influence" that become effective through this unique detector function of the active cerebral cortex. It will be noted that this hypothesis assumes that the "will" or "mind influence" has itself some spatio-temporal patterned character in order to allow it this operative effectiveness.

The Physical Implications of the Hypothesis

When considering the manner in which mind could operate on matter, EDDINGTON (1939) discussed two hypotheses.

(i) It was postulated that mind could control the behaviour of matter within the limits imposed by HEISENBERG'S Principle of Uncertainty (cf. EDDINGTON, 1935). EDDINGTON rejected this partly because the permitted range would be exceedingly small. Presumably he was thinking of an object as large as a neurone. However, a neurophysiologist would now consider the much smaller synaptic vesicle (cf. Figs. 3, 4, 31) as the key structure on which a "mind influence" might work. The synaptic vesicle is approximately a sphere 400 A in diameter and so would have .9 mass of about 3 x 10-17 g. If, as EDDINGTON implies, the uncertainty principle is applicable to an object of this size, then it may be calculates that there is an uncertainty in the position of such an object of abou~ 50 A in I millisecond. These values are of interest since 50 A is approximately the thickness of the presynaptic membrane across which the vesicle discharges its content of specific transmitter substance.

Furthermore, as shown above, minute "influences" thus exerted or a large population of neurones would be rapidly integrated in the forn: of a changed spatiotemporal pattern of activity in the neuronal net There is thus in the active cortex a mechanism that could enormously amplify minute effects exerted on the individual synaptic vesicles, provides of course, as postulated above, these influences have some "meaningful' pattern and are not random. It is therefore possible that the permitted range of behaviour of a synaptic vesicle may be adequate to allow for the effective operation of the postulated "mind influences" on the active cerebral cortex. However, EDDINGTON rejected this hypothesis for the further reason that it involved a fundamental inconsistency. First behaviour according to chance was postulated in making a calculation of the permitted limits according to the uncertainty principle, then it was restricted or controlled by a non-chance or volitional action (the mind influence), which necessarily must be introduced if mind is to be able to take advantage of the latitude allowed by the uncertainty.

(ii) As a consequence of this rejection, EDDINGTON was led to an alternative hypothesis of a correlated behaviour of the individual particles of matter, which he assumed to occur for matter in liaison with mind The behaviour of such matter would stand in sharp contrast to the uncorrelated or random behaviour of particles that is postulated in physics and, as he stated, may be "regarded by us as something outside physics" (EDDINGTON, 1939).

Either of EDDINGTON's hypotheses could serve as the physical basis of the neurophysiological hypothesis that has here been developed for mind-brain liaison. This latter hypothesis of mind-brain liaison has the merits of relating the occasions when the mind can operate on the brain to the observed high level of neuronal activity during consciousness, and of showing how an effective action could be secured by a spatiotemporal pattern of minute "influences." If the neuronal activity of the cerebral cortex is at too low a level, then liaison between mind and brain ceases. The subject is unconscious as in sleep, anaesthesia, coma. Perception and willed action are no longer possible. Furthermore, if a large part of the cerebral cortex is in the state of the rigorous driven activity of a convulsive seizure, there is a similar failure of brain-mind liaison, which is likewise explicable by the deficiency of the sensitive detectors, the critically poised neurones.

General Discussion of Hypothesis of Free-Will

It will be sufficiently evident that the hypotheses here developed are of a fragmentary and tentative character, but it is hoped that they may be of value in further theoretical developments on mind-brain liaison. An outstanding problem for consideration would concern the postulated action of the mind in a spatiotemporal pattern, for presumably it must so act if it is to cause significant modification in patterned activity of the cortex. However, that problem would appear less formidable if there were a sufficiently rapid and detailed feed-back from brain action to mind, which in any case must be assumed for perception.

It will be objected that the essence of the hypothesis is that mind produces changes in the matter-energy system of the brain and hence must be itself in that system (cf. SCHRODINGER, 1951). But this deduction is merely based on the present hypotheses of physics. Since these postulated "mind influences" have not been detected by any existing physical instrument, they have necessarily been neglected in constructing the hypotheses of physics, as was recognized by EDDINGTON (1939). It is at least claimed that the active cerebral cortex conceivably could be a detector of such "influences" even if they existed at an intensity below that detectable by physical instruments.

The present hypotheses would offer an explanation of the high development of matter-mind traffic in the active human cerebral cortex, the development including not only continuous operation but also exquisite subtlety in transmission. Both these features would receive explanation on the basis of the interlocking, integrating, and everchanging pattern of activity formed by the numerous sensitively poised detectors (probably hundreds of millions) that exist in the cortex during states of consciousness

. It should be pointed out that, in the discussion of the functioning of the brain in Chapters 11, III, it has initially been regarded as a "machine" operating according to the laws of physics and chemistry. In conscious states (Chapter IV) it has been shown that it could be in a state of extreme sensitivity as a detector of minute spatio-temporal fields of influence. The hypothesis is here developed that these spatiotemporal fields of influence are exerted by the mind on the brain in willed action. If one uses the expressive terminology of RYLE (1949), the "ghost" operates a "machine," not of ropes and pulleys, valves and pipes, but of microscopic spatio-temporal patterns of activity in the neuronal net woven by the synaptic connections of ten thousand million neurones, and even then only by operating on neurones that are momentarily poised close to a just threshold level of excitability. It would appear that it is the sort of machine a "ghost" could operate, if by ghost we mean in the first place an "agent" whose action has escaped detection even by the most delicate physical instruments.

But even if the hypotheses of brain-mind liaison here developed are on the right track, they are still extremely inadequate. For example, we have no concept of the nature of the mind that could exert these "ghost-like" influences. Again, the slight and irregular telepathic communications being excepted, it is not possible to answer the question: how is it that a given self is in liaison exclusively with a given brain? A further problem concerns the presumed spatiotemporal patterning of the mind. For example, is this altered, as may be operatively desirable, as the microstructure of the brain alters with developing experience and the consequent storage of memories?

2. Freedom and Creativity

It would be generally accepted that creative imagination is the most profound of human activities. It provides the illumination of a new insight or understanding. In science, creative imagination gives that revelation of a new hypothesis embracing and transcending the older hypotheses. There is an immediate aesthetic appeal in its simplicity and scope. Nevertheless it has to be subjected to rigorous criticism and experimental testing. In the most striking examples the illumination has had the suddenness of a flash, as with KEKULE and the benzene ring, DARWIN and the theory of evolution, HAMILTON and his equations. Yet with most of the great scientific hypotheses there was not this instantaneous and apparently miraculous birth of a "brain child." Rather were they developed in stages, being perfected and shaped by critical reason, as with PLANCK and the quantum theory and with EINSTEIN and the theory of relativity. Nor is the suddenness of illumination any guarantee of the validity of a hypothesis. I have had only one such sudden illumination — the so-called Golgi-cell hypothesis of inhibition (BROOKS and ECCLES, 1947) — and some years later it was proved false (ECCLES, 1953)!

If I reflect on the happenings during a scientific investigation, I find that there is incessant "traffic" between my conscious experiences and the objects and events in the external world. For example, from the framework of scientific knowledge I derive some ideas about what I should observe under certain experimental conditions. I plan these conditions and then by means of controlled movements proceed to actualize these conditions. My observations or conscious experiences of the ensuing results are correlated and evaluated in rational and critical thought against my original ideas, and further experiments are planned and executed, and so on. The consequence is that my scientific ideas or hypotheses are enriched, or changed or falsified. My scientific activity is thus seen to be essentially an affair of my rational and conceptual thought together with my exercise of willed movement and my sensory perception.

Before attempting to picture the brain activities that underlie creative imagination, it is important to realize that such illuminations, whether flash-like or with a more gradual and controlled development, come only to minds that have been prepared by the assimilation and critical evaluation of the knowledge in that particular field. One can deliberately seek to experience some new imaginative insight by pouring into one's mind hypotheses and the related experiments and then relax to give opportunity for the subconscious processes that may lead to the illumination in consciousness of a new insight. Such illuminations are often fragmentary and require conscious modification, or so erroneous as to invite immediate rejection by critical reason. Nevertheless, they all give evidence of the creativeness of the subconscious mind.

It may now be asked: what kind of activity is occurring in the brain during this creative activity of the subconscious mind, and how eventually does this creative activity flash into consciousness? Let us consider firstly the pre-requisites for such cerebral action. The wealth of stored memories and critical evaluations implies that in the neuronal network there is an enormous development of complex highly specialized engrams (cf Chapter III) whose permanency derives from the postulated increases in synaptic efficacy. We may say that these "plastic" patterns give the know-how of the brain. We become expert in some fields of knowledge by virtue of the wealth and sublety of engrams that may extend over the greater part of the cortex. When pondering deeply on some problem in this field there must be an unimaginably complex and vivid interplay in the activated patterns. One can speculate further that some failure in the synthesis of these patterns or some conflict in their inter-relationship is the neuronal counterpart of a problem that clamours for solution.

Such are the pre-requisites leading to creative insight. We may surmise that the "subconscious operation of the mind" is dependent on the continued intense interplay of these patterns of neuronal activation. We have seen (Chapter III) that on repeated activation of any neuronal pattern there tends to be a progressive change in the basic plastic pattern or engram, particularly on account of interactions with other patterns. Thus we can expect that new emergent patterns will arise during the subconscious operation of the mind. Should an emergent pattern have an organization that combines and transcends the existent patterns we may expect some resonant-like intensification of activity in the cortex, which would bring the new transcendent pattern to conscious attention, where it would appear as a bright new idea born of creative imagination.

Then begins the process of conscious criticism and evaluation, which seeks to discover flaws in the new idea, and also to discover if it is consistent with the existing knowledge. This done, there comes the crucial stage of the design and carrying out of experiments that test predictions derived from the new idea. We may say that a creative imagination is particularly fruitful if it develops new hypotheses that are remarkable for their generality and for the manner in which they stand up to crucial experimental tests.

Finally, we may ask: what are the characteristics of a brain that exhibits remarkable power of creative imagination? In attempting an answer we are more than ever in the realm of speculation, but certain general statements can be made, though their inadequacy is all too apparent. There must, firstly, be an adequate number of neurones, and. more importantly, there should be a wealth of synaptic connection between them, so that there is, as it were, the structural basis for an immense range of patterns of activity. It is here that the inadequacy of explanation is so evident. There is but a poor correlation between brain size and intelligence, but in this assessment one is assuming a proportionality of brain size and neurone population. Furthermore, a chimpanzee brain may have a neurone population as high as 70% of a human brain, yet it displays almost no creative imagination. Secondly, there should be a particular sensitivity of the synapses to increase their function with usage (cf. Chapter 111) so that memory patterns or engrams are readily formed and are enduring. Both of these properties will ensure that eventually there is built up in the brain an immense wealth of engrams of highly specific character. If added to this there is a peculiar potency for unresting activity in these engrams so that the spatiotemporal patterns are continually being woven in most complex and interacting forms, the stage is set for the deliverance of a "brain child" that is sired, as we say, by creative imagination.

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