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Mortimer Adler
Rogers Albritton
Alexander of Aphrodisias
Samuel Alexander
William Alston
Louise Antony
Thomas Aquinas
David Armstrong
Harald Atmanspacher
Robert Audi
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
Michael Burke
Joseph Keim Campbell
Rudolf Carnap
Ernst Cassirer
David Chalmers
Roderick Chisholm
Randolph Clarke
Samuel Clarke
Anthony Collins
Antonella Corradini
Diodorus Cronus
Jonathan Dancy
Donald Davidson
Mario De Caro
Daniel Dennett
Jacques Derrida
René Descartes
Richard Double
Fred Dretske
John Dupré
John Earman
Laura Waddell Ekstrom
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
Nicholas St. John Green
H.Paul Grice
Ian Hacking
Ishtiyaque Haji
Stuart Hampshire
Sam Harris
William Hasker
Georg W.F. Hegel
Martin Heidegger
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
Michael Levin
George Henry Lewes
David Lewis
Peter Lipton
C. Lloyd Morgan
John Locke
Michael Lockwood
E. Jonathan Lowe
John R. Lucas
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
Thomas Nagel
Otto Neurath
Friedrich Nietzsche
John Norton
Robert Nozick
William of Ockham
Timothy O'Connor
David F. Pears
Charles Sanders Peirce
Derk Pereboom
Steven Pinker
Karl Popper
Huw Price
Hilary Putnam
Willard van Orman Quine
Frank Ramsey
Ayn Rand
Michael Rea
Thomas Reid
Charles Renouvier
Nicholas Rescher
Richard Rorty
Josiah Royce
Bertrand Russell
Paul Russell
Gilbert Ryle
Jean-Paul Sartre
Kenneth Sayre
Moritz Schlick
Arthur Schopenhauer
John Searle
Wilfrid Sellars
Alan Sidelle
Ted Sider
Henry Sidgwick
Walter Sinnott-Armstrong
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
G.H. von Wright
David Foster Wallace
R. Jay Wallace
Ted Warfield
Roy Weatherford
William Whewell
Alfred North Whitehead
David Widerker
David Wiggins
Bernard Williams
Timothy Williamson
Ludwig Wittgenstein
Susan Wolf


Michael Arbib
Walter Baade
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
Lüder Deecke
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
Philipp Frank
Lila Gatlin
Michael Gazzaniga
GianCarlo Ghirardi
J. Willard Gibbs
Nicolas Gisin
Paul Glimcher
Thomas Gold
Brian Goodwin
Joshua Greene
Jacques Hadamard
Patrick Haggard
Stuart Hameroff
Augustin Hamon
Sam Harris
Hyman Hartman
John-Dylan Haynes
Donald Hebb
Martin Heisenberg
Werner Heisenberg
John Herschel
Art Hobson
Jesper Hoffmeyer
E. T. Jaynes
William Stanley Jevons
Roman Jakobson
Pascual Jordan
Ruth E. Kastner
Stuart Kauffman
Martin J. Klein
Simon Kochen
Hans Kornhuber
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
John McCarthy
Ulrich Mohrhoff
Jacques Monod
Emmy Noether
Abraham Pais
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
John Stachel
Henry Stapp
Tom Stonier
Antoine Suarez
Leo Szilard
Max Tegmark
William Thomson (Kelvin)
Peter Tse
Vlatko Vedral
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
Fritz Zwicky


Free Will
Mental Causation
James Symposium
Max Delbrück

Max Delbrück was a physicist turned biophysicist as a result of Niels Bohr's lectures on complementarity and "Light and Life." Bohr suggested a complementary relation between the physical and physiological analogous to that between the wave and particle views in quantum mechanics.

Although he never found the equivalent of an uncertainty principle in biology, Delbrück's research into bacteriophages (viruses) in the 1930's and early 1940's won him the Nobel prize for discovering that bacteria become resistant to viruses as a result of genetic mutations.

This emphasis on mutations led Erwin Schrödinger to devote a large part of his 1945 essay "What Is Life?" to Delbrück's work, which made him famous very quickly. Schrödinger guessed that the genetic hereditary material might be an "aperiodic crystal" and this inspired James Watson and Francis Crick to discover the double helix architecture of DNA.

The 1986 book, Mind from Matter?, was edited posthumously from audio tapes of Delbrück's CalTech biology course, given in the mid 1970's. The course included twenty lectures that he called "evolutionary epistemology." It is unlikely that Delbrück knew of the similarly titled work of Donald Campbell or Karl Popper (or vice versa).

We begin our epistemological inquiry from the viewpoint of naive realism and consider our problem of truth and reality in the light of evolution.

So we ask three naive questions:

1. How can we construct a theory of a universe without life, and therefore without mind, and then expect life and mind to evolve, somehow, from this lifeless and mindless beginning?

2. How can we conceive of the evolution of organisms with mind strictly as an adaptive response to selective pressures favoring specimens able to cope with life in the cave, and then expect that this mind is capable of elaborating the most profound insights into mathematics, cosmology, matter, and the general organization of life and mind itself?

3. Indeed, does it even make sense to posit that the capacity to know truth can arise from dead matter?

The principal adaptive response that Delbrück studied was the basis of perception, which is needed to understand awareness of the environment, the picture of the environment stored in the mind as information about experience, and ultimately the consciousness of the mind.
The unity and continuity of life on earth is manifest in its molecular anatomy. All modern forms of life use nucleic acids as information stores and proteins as agents for the direction of biochemical reactions, with the same processes of transcription and translation mediating the expression of the stored information. The protein and nucleic acid constituents are universal, as is the genetic code, which determines how information stored as nucleotide sequences in long nucleic acid molecules is translated into the amino acid sequences of proteins. Eukaryotes and prokaryotes also share certain special molecules, for instance heme for electron transport, chlorophyll for photosynthesis, ATP for energy storage, and riboflavin for the catalysis of oxidation-reduction reactions and for sensing the presence of light.

The unity and continuity of life is equally manifest in its psychic aspects. Perception in plants and animals is a familiar phenomenon, but the beginnings of perception are also clearly present in microorganisms, in which adaptive behavior demonstrates that they can detect and evaluate signals from the environment and respond appropriately. For example, chemoreception — the ability to sense and respond to changes in the chemical composition of the environment — is manifest in the swimming pattern of chemotactic bacteria. The path of a swimming bacterium corresponds to a random walk: runs of orderly swimming along a straight path are interrupted from time to time by a tumbling motion, resulting in the random selection of a new direction for the next straight run.

If chemotactic bacteria are in a medium in which there is a gradient of favorable (attractant) or unfavorable (repellent) chemicals, the selection of the new swimming direction following each tumble is still random, but the intervals between tumbles are longer when the path of the straight run is up the attractant or down the repellent gradient. In this way, the overall direction of the random swim becomes biased toward higher concentration of an attractant or lower concentration of a repellent. The perception of light in prokaryotes is exemplified by the phototaxis, or active avoidance of dark regions in their environment, of photosynthetic bacteria. There are at least two ways in which bacterial phototaxis is accomplished: one of them is a stochastic response consisting of a biased random walk similar to chemotaxis; the other is a deterministic response. Bacteria controlled by the stochastic response, upon sensing that they are swimming down a light gradient, simply stop swimming until Brownian motion gives them a new direction, and then they start swimming again. In this way, the overall path of the random swim is biased in the direction of higher light intensity. Bacteria controlled by the deterministic response are able to swim both forward and backward. If such bacteria sense that they are swimming into regions of lower light intensity, they simply shift into reverse and swim backward into regions of higher light intensity.

Many primitive eukaryotic organisms manifest the deterministic growth response to light called phototropism. The fungus Phycomyces, for example, does not resort to photosynthesis as an energy source; however, it resorts to phototropism to guide the growth of the stalk toward the light source and thus places its fruiting bodies at the tip of the stalk in position for optimal dispersal of its spores. The stalk of the fruiting body is actually a cylindrical lens capable of focusing light, which allows the fungus to sense the direction of maximum illumination. Phycomyces can also sense ' gravity, which allows it to grow its stalk in a consistently upward direction (negative geotropism). Finally, Phycomyces can detect the presence of a solid surface. Irrespective of illumination, the fungus senses the presence of such a surface at a distance of about a millimeter and grows away from it. Just how Phycomyces accomplishes this act of perception is . not understood, although it probably involves the emission and absorption of a gaseous or volatile substance either produced by Phycomyces or present in the environment.

In the examples of primitive perception considered here, the detection of the signal — chemical attractant or light — involves an adaptation mechanism similar to the dark adaptation of our eyes: the organism sets its level of detection in accordance with the average strength of the stimulus (such as the concentration of chemical or the intensity of light). Thus we have in these single-celled organisms all three components of the perceptive process of higher forms of life: stochastic response, deterministic response, and adaptive response based on immediate past experience. It is a long way, however, from these primitive perceptive processes and their evaluation of environmental signals to the machinery involved in, for example, the decision of a young man to propose marriage to his girlfriend. He responds to her charm with his emotional brain (the mid-brain) and his thinking brain (the cerebral cortex). His decision is influenced by his genes, by his imprinting in earliest childhood, by his identity as it detached itself from his mother, by his moral upbringing, by his economlc circumstances, and by his surging sex drive.

Delbrück wonders how much progress he has made on explaining how mind evolved from matter, and the fundamental mind-body problem that he called the "Cartesian Cut."
Have we, then, answered the naive question we posed at the outset? Did we explain how mind evolved from no mind? Did we find out why so much more was delivered than was ordered, that is, how the mind, having evolved for using stone tools, mounting a minimum of social organization for the hunt, and telling tales about hunting around the hearth, managed to get us to the abstruse reaches of number theory, relativity and quantum theory, elementary particles, and molecular genetics, not to speak of getting us to the moon? Maybe we didn't give any straight answers to these questions, but I think the dilemma "mind from no mind" looks less perplexing than it used to. On the one hand, neurobiological and psychophysical studies of subjective perception have provided insights into how we come to know the world, and cybernetics and even AI have helped a little to illuminate the nature of human thought processes. On the other hand, our ideas about the objective character of the physical world, and hence of the nature of truth have been revised. In other words, mind looks less psychic and matter looks less materialistic, especially in the light of Bohr's complementarity argument, which removed the illusion of total determination and objectivity.

Part, but only part, of the solution to the riddle of how it is possible for the mind to deal so successfully with aspects of the world for dealing with which it was never selected may lie in a combination of fluctuation and illusion. The fluctuation arises from the vast amplification of simple knowledge through social organization. To fly to the moon does not require monumental intelligence; it requires the cooperation of 500,000 quite ordinary minds. The illusion arises from the preoccupation with our successes and the repression of our failures. The Stone Age people in England constructed Stonehenge 4000 to 5000 years ago, embodying some astronomical information in its architecture. They probably thought very highly of themselves. Little did they know how much they didn't know.

Let us conclude with some general reflections on the peculiar role played by the sciences in this story. The classical natural sciences solidified the feeling that the adult human mind is an absolute: it grasps absolute physical laws concerned with absolute matter embedded in absolute space and time. The Cartesian cut between mind and matter is the rock on which such physical laws stand.

Modern science has gone in the opposite direction. It has forced us to abandon absolute space and time, determinism, and the absolute object. It has shown that these naive notions are applicable only in the middle dimensions of space, time, and energy and must be replaced by more abstract formal schemes. As soon as we move to phenomena at extreme dimensions, our intuitions—that is, our concrete mental operations— become inadequate. This is the point, exactly, where evolutionary thinking is decisively helpful. It suggests, in fact it demands, that our concrete mental operations are indeed adaptations to the mode of life in which we had to compete for survival a long time before the development of science. As such we are saddled with them, just as we are with our organs of locomotion and our eyes and ears. But with science we can transcend our intuitions, just as with electronics we can transcend our eyes and ears.

To the question of how the mental capacity for such transcendence can have arisen in the course of biological evolution I have no satisfactory answer. Indeed, the approach I have sketched in this essay by no means resolves all puzzles, nor does it produce a grand synthesis of the diverse universes of discourse now current in the various sciences. Least of all does it give a basis for a new setting of values in ethics relevant to the life of the individual or to social organization.

The feeling of absurdity evoked by the question "mind from matter?" is perhaps similar to the feeling of absurdity with which we have learned to cope when we permit relativity theory to alter our intuitive concepts of time and space and quantum theory to alter our intuitive concepts of object and causality. If we can learn to accept this ultimate absurdity, there may yet be hope for developing a formal approach that will permit a grand synthesis.

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