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 Barrett William Belsham Henri Bergson George Berkeley Isaiah Berlin Richard J. Bernstein Bernard Berofsky Robert Bishop Max Black Susanne Bobzien Emil du BoisReymond Hilary Bok Laurence BonJour George Boole Émile Boutroux Daniel Boyd F.H.Bradley C.D.Broad Michael Burke Lawrence Cahoone C.A.Campbell Joseph Keim Campbell Rudolf Carnap Carneades Nancy Cartwright Gregg Caruso Ernst Cassirer David Chalmers Roderick Chisholm Chrysippus Cicero Tom Clark 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 Austin Farrer Herbert Feigl Arthur Fine John Martin Fischer Frederic Fitch Owen Flanagan Luciano Floridi Philippa Foot Alfred Fouilleé Harry Frankfurt Richard L. Franklin Bas van Fraassen 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 Frank Jackson William James Lord Kames Robert Kane Immanuel Kant Tomis Kapitan Walter Kaufmann Jaegwon Kim William King Hilary Kornblith Christine Korsgaard Saul Kripke Thomas Kuhn Andrea Lavazza Christoph Lehner Keith Lehrer Gottfried Leibniz Jules Lequyer Leucippus Michael Levin Joseph Levine George Henry Lewes C.I.Lewis David Lewis Peter Lipton C. Lloyd Morgan John Locke Michael Lockwood Arthur O. Lovejoy E. Jonathan Lowe John R. Lucas Lucretius Alasdair MacIntyre Ruth Barcan Marcus Tim Maudlin James Martineau Nicholas Maxwell 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 Otto Neurath Friedrich Nietzsche John Norton P.H.NowellSmith Robert Nozick William of Ockham Timothy O'Connor Parmenides David F. Pears Charles Sanders Peirce Derk Pereboom Steven Pinker U.T.Place 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 JeanPaul Sartre Kenneth Sayre T.M.Scanlon Moritz Schlick John Duns Scotus Arthur Schopenhauer John Searle Wilfrid Sellars David Shiang Alan Sidelle Ted Sider Henry Sidgwick Walter SinnottArmstrong Peter Slezak 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 C.F. von Weizsäcker William Whewell Alfred North Whitehead David Widerker David Wiggins Bernard Williams Timothy Williamson Ludwig Wittgenstein Susan Wolf Scientists David Albert Michael Arbib Walter Baade Bernard Baars Jeffrey Bada Leslie Ballentine Marcello Barbieri Gregory Bateson Horace Barlow John S. Bell Mara Beller Charles Bennett Ludwig von Bertalanffy Susan Blackmore Margaret Boden David Bohm Niels Bohr Ludwig Boltzmann Emile Borel Max Born Satyendra Nath Bose Walther Bothe Jean Bricmont Hans Briegel Leon Brillouin Stephen Brush Henry Thomas Buckle S. H. Burbury Melvin Calvin Donald Campbell Sadi Carnot Anthony Cashmore Eric Chaisson Gregory Chaitin JeanPierre Changeux Rudolf Clausius Arthur Holly Compton John Conway Jerry Coyne John Cramer Francis Crick E. P. Culverwell Antonio Damasio Olivier Darrigol Charles Darwin Richard Dawkins Terrence Deacon Lüder Deecke Richard Dedekind Louis de Broglie Stanislas Dehaene Max Delbrück Abraham de Moivre Bernard d'Espagnat Paul Dirac Hans Driesch John Eccles Arthur Stanley Eddington Gerald Edelman Paul Ehrenfest Manfred Eigen Albert Einstein George F. R. Ellis Hugh Everett, III Franz Exner Richard Feynman R. A. Fisher David Foster Joseph Fourier Philipp Frank Steven Frautschi Edward Fredkin Benjamin GalOr Howard Gardner Lila Gatlin Michael Gazzaniga Nicholas GeorgescuRoegen GianCarlo Ghirardi J. Willard Gibbs James J. Gibson Nicolas Gisin Paul Glimcher Thomas Gold A. O. Gomes Brian Goodwin Joshua Greene Dirk ter Haar Jacques Hadamard Mark Hadley Patrick Haggard J. B. S. Haldane Stuart Hameroff Augustin Hamon Sam Harris Ralph Hartley Hyman Hartman Jeff Hawkins JohnDylan Haynes Donald Hebb Martin Heisenberg Werner Heisenberg John Herschel Basil Hiley Art Hobson Jesper Hoffmeyer Don Howard John H. Jackson William Stanley Jevons Roman Jakobson E. T. Jaynes Pascual Jordan Eric Kandel Ruth E. Kastner Stuart Kauffman Martin J. Klein William R. Klemm Christof Koch Simon Kochen Hans Kornhuber Stephen Kosslyn Daniel Koshland Ladislav Kovàč Leopold Kronecker Rolf Landauer Alfred Landé PierreSimon Laplace Karl Lashley David Layzer Joseph LeDoux Gerald Lettvin Gilbert Lewis Benjamin Libet David Lindley Seth Lloyd Werner Loewenstein Hendrik Lorentz Josef Loschmidt Alfred Lotka Ernst Mach Donald MacKay Henry Margenau Owen Maroney David Marr Humberto Maturana James Clerk Maxwell Ernst Mayr John McCarthy Warren McCulloch N. David Mermin George Miller Stanley Miller Ulrich Mohrhoff Jacques Monod Vernon Mountcastle Emmy Noether Donald Norman Alexander Oparin Abraham Pais Howard Pattee Wolfgang Pauli Massimo Pauri Wilder Penfield Roger Penrose Steven Pinker Colin Pittendrigh Walter Pitts Max Planck Susan Pockett Henri Poincaré Daniel Pollen Ilya Prigogine Hans Primas Zenon Pylyshyn Henry Quastler Adolphe Quételet Pasco Rakic Nicolas Rashevsky Lord Rayleigh Frederick Reif Jürgen Renn Giacomo Rizzolati A.A. Roback Emil Roduner Juan Roederer Jerome Rothstein David Ruelle David Rumelhart Robert Sapolsky Tilman Sauer Ferdinand de Saussure Jürgen Schmidhuber Erwin Schrödinger Aaron Schurger Sebastian Seung Thomas Sebeok Franco Selleri Claude Shannon Charles Sherrington Abner Shimony Herbert Simon Dean Keith Simonton Edmund Sinnott B. F. Skinner Lee Smolin Ray Solomonoff Roger Sperry John Stachel Henry Stapp Tom Stonier Antoine Suarez Leo Szilard Max Tegmark Teilhard de Chardin Libb Thims William Thomson (Kelvin) Richard Tolman Giulio Tononi Peter Tse Alan Turing C. S. Unnikrishnan Francisco Varela Vlatko Vedral Vladimir Vernadsky Mikhail Volkenstein Heinz von Foerster Richard von Mises John von Neumann Jakob von Uexküll C. H. Waddington John B. Watson Daniel Wegner Steven Weinberg Paul A. Weiss Herman Weyl John Wheeler Jeffrey Wicken Wilhelm Wien Norbert Wiener Eugene Wigner E. O. Wilson Günther Witzany Stephen Wolfram H. Dieter Zeh Semir Zeki Ernst Zermelo Wojciech Zurek Konrad Zuse Fritz Zwicky Presentations Biosemiotics Free Will Mental Causation James Symposium 
Quantum Physics
Some Background
From the earliest days of quantum theory, when Max Planck in 1900 hypothesized an abstract "quantum of action" and Albert Einstein in 1905 hypothesized that energy comes in discrete physical quanta, there have been disagreements about "interpretations," misunderstandings about the underlying "reality" of the external world that could account for the apparent agreement between quantum theory and the observed experimental facts, without abandoning the classical physics ideas of continuity, causality, and determinism. For example, Planck, the inventor of the quantum of action, used his constant h as a heuristic device to calculate the probabilities of various virtual oscillators (distributing them among energy states using Boltzmann's statistical mechanics ideas, the partition function, etc.). He quantized these mechanical oscillators, but not the radiation field itself. In 1913, Bohr similarly quantized the oscillators (electrons) in the "old quantum theory" and his planetary model of the electrons orbiting the Rutherford nucleus. Bohr's electrons "jump" discontinuously from orbit to orbit, emitting or absorbing discrete amounts of energy E_{n}  E_{m} where n and m are orbital "quantum numbers." But Bohr insisted that the energy radiated in a quantum jump was continuous, ignoring, even rejecting, Einstein's lightquantum hypothesis.
In 1905, Einstein wrote, "the energy of a light ray spreading out from a point source is not continuously distributed over an increasing space but consists of a finite number of energy quanta which are localized at points in space, which move without dividing, and which can only be produced and absorbed as whole units." It was Einstein, not Planck, who made quantum mechanics discrete and indeterministic.
By comparison to Planck, Einstein had already in 1905 quantized the continuous electromagnetic radiation field as light quanta (today's photons). Planck denied the physical "reality" of any quanta (including his own virtual oscillators) until 1910 at the earliest. And Bohr did not accept discrete photons as being emitted and absorbed during quantum jumps until twenty years after Einstein proposed them  if then. Photons are now universally accepted, of course, and (sadly) standard quantum mechanics says they are emitted and absorbed during Bohr's "quantum jumps" of the electrons.
Einstein saw clearly that if the radiation emitted by an atom were to spread out diffusely as a classical wave into a large volume of space, how could the energy collect itself together again instantly to be absorbed by another atom  without having that energy travel faster than light speed as it gathered itself together in the absorbing atom? He clearly saw that a discrete, discontinuous "jump" was involved, something denied by many of the modern "interpretations" of quantum mechanics.
Einstein feared that if energy spread out in space had to move instantly to a given point, it would violate his principle of relativity. Thus began the conflict between quantum mechanics and relativity
He also saw that the wave that filled space moments before the detection of the whole quantum of energy must disappear instantly as all the energy in the quantum is absorbed by a single atom in a particular location. This was seen as a 'collapse" of a light wave twenty years before there was a "wave function" and Erwin Schrōdinger's wave equation! Later Einstein interpreted the wave at a point as the probability of light quanta at that point, many years before the socalled "Born Rule." Max Born said many times that his "statistical interpretation" of the wave function was based on Einstein's original suggestion.
It was not Born who first interpreted the wave function as giving us probabilities. It was Einstein. The idea of something (later called the wave function) associated with the particle led to the problem of waveparticle duality, described first by Einstein in 1909. In 1927, he expressed concern that what came to be called nonlocality violates his special theory of relativity. To this day, it is the idea that quantum physics cannot be reconciled with relativity. The nadir of interpretation was probably the most famous interpretation of all, the one developed in Copenhagen, the one Niels Bohr's assistant Leon Rosenfeld said was not an interpretation at all, but simply the "standard orthodox theory" of quantum mechanics. It was the nadir of interpretation because Copenhagen wanted to put a stop to "interpretation" in the sense of understanding or "visualizing" an underlying reality. The Copenhageners said we should not try to "visualize" what is going on behind the collection of observable experimental data. Just as Kant said we could never know anything about the "thing in itself," the Dingansich, so the positivist philosophy of Comte, Mach, Russell, and Carnap and the British empiricists Locke and Hume claim that knowledge stops at the "secondary" sense data or perceptions of phenomena, preventing access to the primary "objects." Einstein's views on quantum mechanics have been seriously distorted (and his early work largely forgotten), perhaps because of his famous criticisms of Born's "statistical interpretation" and Werner Heisenberg's claim that quantum mechanics was "complete" without describing what particles are doing from moment to moment. Though its foremost critic, Einstein frequently said that quantum mechanics was a most successful theory, the very best theory so far at explaining microscopic phenomena, but that he hoped his ideas for a continuous field theory would someday add to the discrete particle theory and its "nonlocal" phenomena. It would allow us to get a deeper understanding of underlying reality, though at the end he despaired for his continuous field theory compared to particle theories. Many of the "interpretations" of quantum mechanics deny a central element of quantum theory, one that Einstein himself established in 1916, namely the role of indeterminism, or "chance," to use its traditional name, as Einstein did in physics (in German, Zufall) and as William James did in philosophy in the 1880's. These interpretations hope to restore the determinism of classical mechanics. Einstein hoped for a return to deterministic physics, but even more important for him was a physics based on continuous fields, rather than discrete discontinuous particles. We can therefore classify various interpretations by whether they accept or deny chance, especially in the form of the socalled "collapse" of the wave function, also known as the "reduction" of the wave packet or what Paul Dirac called the "projection postulate." Most "nocollapse" theories are deterministic. "Collapses" in standard quantum mechanics are irreducibly indeterministic. Many interpretations are attempts to wrestle with still another problem that Einstein saw as early as 1905, in "nonlocal" events something appears to be moving faster than light and thus violating his special theory of relativity (which he formulated in 1905). So we can classify interpretations by whether they accept the instantaneous nature of the collapse, especially the collapse of the twoparticle wave function of "entangled" systems, where two particles appear instantly in widely separated places, with correlated properties that conserve energy, momentum, angular momentum, spin, etc. These interpretations are concerned about nonlocality  the idea that "reality" is "nonlocal" with simultaneous events in widely separated places correlated perfectly  a sort of "actionatadistance." Many interpretations prefer wave mechanics to quantum mechanics, seeing wave theories as continuous field theories. They like to regard the wave function as a real entity rather than an abstract possibilities function. De Broglie's pilotwave theory and its variations (e.g., Bohmian mechanics, Schrödinger's view) hoped to represent the particle as a "wave packet" composed of many waves of different frequencies, such that the packet has nonzero values in a small volume of space. Schrödinger and others found such a wave packet rapidly disperses . Finally, we may also classify interpretations by their definitions of what constitutes a "measurement," and particularly what they see as the famous "problem of measurement." Niels Bohr, Werner Heisenberg, and John von Neumann had a special role for the "conscious observer"in a measurement. Eugene Wigner claimed that the observer's conscious mind caused the wave function to collapse in a measurement. So we have three major characterizations  indeterministicdiscretediscontinuous "collapse" vs. deterministiccontinuous "nocollapse" theories, nonlocalityfasterthanlight vs. local "elements of reality" in "realistic theories, and the role of the observer. Another way to look at an interpretation is to ask which basic element (or elements) of standard quantum mechanics does the interpretation question or just deny? For example, some interpretations deny the existence of particles. They admit only waves that evolve unitarily under the Schrōdinger equation. We can begin by describing those elements, using the formulation of quantum mechanics that Einstein thought most perfect, that of P. A. M. Dirac.
A Brief Introduction to Basic Quantum Mechanics
Einstein said of Dirac in 1930,
"Dirac, to whom, in my opinion, we owe the most perfect exposition, logically, of this
All of quantum mechanics rests on the Schrōdinger equation of motion
that deterministically describes the time evolution of the
probabilistic wave function, plus three basic
assumptions, the principle of superposition (of wave functions), the
axiom of measurement (of expectation values for observables), and the projection
postulate (which describes the collapse of the wave function that introduces indeterminism or chance during interactions).
[quantum] theory" Dirac's "transformation theory" then allows us to "represent" the initial wave function (before an interaction) in terms of a "basis set" of "eigenfunctions" appropriate for the possible quantum states of our measuring instruments that will describe the interaction. Elements in the "transformation matrix" immediately give us the probabilities of measuring the system and finding it in one of the possible quantum states or "eigenstates," each eigenstate corresponding to an "eigenvalue" for a dynamical operator like the energy, momentum, angular momentum, spin, polarization, etc. Diagonal (n, n) elements in the transformation matrix give us the eigenvalues for observables in quantum state n. Offdiagonal (n, m) matrix elements give us transition probabilities between quantum states n and m. Notice the sequence  possibilities > probabilities > actuality: the wave function gives us the possibilities, for which we can calculate probabilities. Each experiment gives us one actuality. A very large number of identical experiments confirms our probabilistic predictions to thirteen significant figures (decimal places), the most accurate physical theory ever discovered. The fundamental equation of motion in quantum mechanics is Erwin Schrōdinger's famous wave equation that describes the evolution in time of his wave function ψ.
iℏ δψ / δt = H ψ (1)
Max Born interpreted the square of the absolute value of Schrōdinger's wave function ψ_{n} ^{2} (or < ψ_{n}  ψ_{n} > in Dirac notation) as providing the probability of finding a quantum system in a particular state n. As long as this absolute value (in Dirac braket notation) is finite,
< ψ_{n}  ψ_{n} > ≡ ∫ ψ* (q) ψ (q) dq < ∞, (2)
then ψ can be normalized, so that the probability of finding a particle somewhere < ψ  ψ > = 1, which is necessary for its interpretation as a probability. The normalized wave function can then be used to calculate "observables" like the energy, momentum, etc. For example, the probable or expectation value for the position r of the system, in configuration space q, is
< ψ  r  ψ > = ∫ ψ* (q) r ψ (q) dq. (3)
2. The Principle of Superposition. The Schrōdinger equation (1) is a linear equation. It has no quadratic or higher power terms, and this introduces a profound  and for many scientists and philosophers a disturbing  feature of quantum mechanics, one that is impossible in classical physics, namely the principle of superposition of quantum states. If ψ_{a} and ψ_{b} are both solutions of equation (1), then an arbitrary linear combination of these,
 ψ > = c_{a}  ψ_{a} > + c_{b}  ψ_{b} >, (4)
with complex coefficients c_{a} and c_{b}, is also a solution. Together with Born's probabilistic (statistical) interpretation of the wave function, the principle of superposition accounts for the major mysteries of quantum theory, some of which we hope to resolve, or at least reduce, with an objective (observerindependent) explanation of irreversible information creation during quantum processes. Observable information is critically necessary for measurements, though observers can come along anytime after the information comes into existence as a consequence of the interaction of a quantum system and a measuring apparatus. The quantum (discrete) nature of physical systems results from there generally being a large number of solutions ψ_{n} (called eigenfunctions) of equation (1) in its time independent form, with energy eigenvalues E_{n}.
H ψ_{n} = E_{n} ψ_{n}, (5)
The discrete spectrum energy eigenvalues E_{n} limit interactions (for example, with photons) to specific energy differences E_{n}  E_{m}. In the old quantum theory, Bohr postulated that electrons in atoms would be in "stationary states" of energy E_{n}, and that energy differences would be of the form E_{n}  E_{m} = hν, where ν is the frequency of the observed spectral line. Einstein, in 1916, derived these two Bohr postulates from basic physical principles in his paper on the emission and absorption processes of atoms. What for Bohr were assumptions, Einstein grounded in quantum physics, though virtually no one appreciated his foundational work at the time, and few appreciate it today, his work eclipsed by the Copenhagen physicists. The eigenfunctions ψ_{n} are orthogonal to each other
< ψ_{n}  ψ_{m} > = δ_{nm} (6)
where the "delta function"
δ_{nm} = 1, if n = m, and = 0, if n ≠ m. (7)  φ > = ∑ _{n = 0} ^{n = ∞} c_{n}  ψ_{n} >. (8) The expansion coefficients are c_{n} = < ψ_{n}  φ >. (9) In the abstract Hilbert space, < ψ_{n}  φ > is the "projection" of the vector φ onto the orthogonal axes ψ_{n} of the ψ_{n} "basis" vector set. 2.1 An example of superposition. Dirac tells us that a diagonally polarized photon can be represented as a superposition of vertical and horizontal states, with complex number coefficients that represent "probability amplitudes." Horizontal and vertical polarization eigenstates are the only "possibilities," if the measurement apparatus is designed to measure for horizontal or vertical polarization. Thus,
 d > = ( 1/√2)  v > + ( 1/√2)  h > (10)
The vectors (wave functions) v and h are the appropriate choice of basis vectors, the vector lengths are normalized to unity, and the sum of the squares of the probability amplitudes is also unity. This is the orthonormality condition needed to interpret the (squares of the) wave functions as probabilities. When these (in general complex) number coefficients (1/√2) are squared (actually when they are multiplied by their complex conjugates to produce positive real numbers), the numbers (1/2) represent the probabilities of finding the photon in one or the other state, should a measurement be made on an initial state that is diagonally polarized. Note that if the initial state of the photon had been vertical, its projection along the vertical basis vector would be unity, its projection along the horizontal vector would be zero. Our probability predictions then would be  vertical = 1 (certainty), and horizontal = 0 (also certainty). Quantum physics is not always uncertain, despite its reputation. The axiom of measurement depends on the idea of "observables," physical quantities that can be measured in experiments. A physical observable is represented as an operator A that is "Hermitean" (one that is "selfadjoint"  equal to its complex conjugate, A* = A). The diagonal n, n elements of the operator's matrix, < ψ_{n}  A  ψ_{n} > = ∫ ∫ ψ* (q) A (q) ψ (q) dq, (11)
The molecule suffers a recoil in the amount of hν/c during this elementary process of emission of radiation; the direction of the recoil is, at the present state of theory, determined by "chance"...
The offdiagonal n, m
elements describe the uniquely quantum
property of interference between
wave functions and provide a measure of
the probabilities for transitions between
states n and m.
The weakness of the theory is, on the one hand, that it does not bring us closer to a linkup with the wave theory; on the other hand, it also leaves time of occurrence and direction of the elementary processes a matter of "chance."
It speaks in favor of the theory that the statistical law assumed for [spontaneous] emission is nothing but the Rutherford law of radioactive decay.
It is the intrinsic quantum probabilities that provide the ultimate source of indeterminism, and consequently of irreducible irreversibility, as we shall see. Transitions between states are irreducibly random, like the decay of a radioactive nucleus (discovered by Rutherford in 1901) or the emission of a photon by an electron transitioning to a lower energy level in an atom (explained by Einstein in 1916). The axiom of measurement is the formalization of Bohr's 1913 postulate that atomic electrons will be found in stationary states with energies E_{n}. In 1913, Bohr visualized them as orbiting the nucleus. Later, he said they could not be visualized, but chemists routinely visualize them as clouds of probability amplitude with easily calculated shapes that correctly predict chemical bonding. The offdiagonal transition probabilities are the formalism of Bohr's "quantum jumps" between his stationary states, emitting or absorbing energy hν = E_{n}  E_{m}. Einstein explained clearly in 1916 that the jumps are accompanied by his discrete light quanta (photons), but Bohr continued to insist that the radiation was classical for another ten years, deliberately ignoring Einstein's foundational efforts in what Bohr might have felt was his area of expertise (quantum mechanics). The axiom of measurement asserts that a large number of measurements of the observable A, known to have eigenvalues A_{n}, will result in the number of measurements with value A_{n} that is proportional to the probability of finding the system in eigenstate ψ_{n}. Quantum mechanics is a probabilistic and statistical theory. The probabilities are theories about what experiments will show. Experiments provide the statistics (the frequency of outcomes) that confirm the predictions of quantum theory  with the highest accuracy of any theory ever discovered! The third novel idea of quantum theory is often considered the most radical. It has certainly produced some of the most radical ideas ever to appear in physics, in attempts by various "interpretations" to deny it. The projection postulate is actually very simple, and arguably intuitive as well. It says that when a measurement is made, the system of interest will be found in (will instantly "collapse" into) one of the possible eigenstates of the measured observable. We have several possibilities for eigenvalues. We can calculate the probabilities for each eigenvalue. Measurement simply makes one of these actual, and it does so, said Max Born, in proportion to the absolute square of the probability amplitude wave function ψ_{n}.
Note that Einstein saw the chance in quantum theory at least ten years before Born
In this way, ontological chance enters physics, and it is partly this fact of quantum randomness that bothered Einstein ("God does not play dice") and Schrōdinger (whose equation of motion for the probabilityamplitude wave function is deterministic). The projection postulate, or collapse of the wave function, is the element of quantum mechanics most often denied by various "interpretations." The sudden discrete and discontinuous "quantum jumps" are considered so nonintuitive that interpreters have replaced them with the most outlandish (literally) alternatives. The famous "manyworlds interpretation" substitutes a "splitting" of the entire universe into two equally large universes, massively violating the most fundamental conservation principles of physics, rather than allow a diagonal photon arriving at a polarizer to suddenly "collapse" into a horizontal or vertical state. 4.1 An example of projection. Given a quantum system in an initial state  φ >, we can expand it in a linear combination of the eigenstates of our measurement apparatus, the  ψ_{n} >.
 φ > = ∑ _{n = 0} ^{n = ∞} c_{n}  ψ_{n} >. (8)
In the case of Dirac's polarized photons, the diagonal state  d > is a linear combination of the horizontal and vertical states of the measurement apparatus,  v > and  h >. When we square the (1/√2) coefficients, we see there is a 50% chance of measuring the photon as either horizontal or vertically polarized.
 d > = ( 1/√2)  v > + ( 1/√2)  h > (10)
4.2 Visualizing projection. When a photon is prepared in a vertically polarized state  v >, its interaction with a vertical polarizer is easy to visualize. We can picture the state vector of the whole photon simply passing through the polarizer unchanged. The same is true of a photon prepared in a horizontally polarized state  h > going through a horizontal polarizer. And the interaction of a horizontal photon with a vertical polarizer is easy to understand. The vertical polarizer will absorb the horizontal photon completely. The diagonally polarized photon  d >, however, fully reveals the nonintuitive nature of quantum physics. We can visualize quantum indeterminacy, its statistical nature, and we can dramatically visualize the process of collapse, as a state vector aligned in one direction must rotate instantaneously into another vector direction.
When we have only one photon at a time, we never get onehalf of a photon coming through the polarizer. Critics of standard quantum theory sometimes say that it tells us nothing about individual particles, only ensembles of identical experiments. There is truth in this, but nothing stops us from imagining the strange process of a single diagonally polarized photon interacting with the vertical polarizer. There are two possibilities. We either get a whole photon coming through (which means that it "collapsed" or the diagonal vector was "reduced to" a vertical vector) or we get no photon at all. This is the entire meaning of "collapse." It is the same as an atom "jumping" discontinuously and suddenly from one energy level to another. It is the same as the photon in a twoslit experiment suddenly appearing at one spot on the photographic plate, where an instant earlier it might have appeared anywhere. We can even visualize what happens when no photon appears. We can imagine that the diagonal photon was reduced to a horizontally polarized photon and was completely absorbed. Why can we see the statistical nature and the indeterminacy? First, statistically, in the case of many identical photons, we can say that half will pass through and half will be absorbed. The indeterminacy is that in the case of one photon, we have no ability to know which it will be. This is just as we cannot predict the time when a radioactive nucleus will decay, or the time and direction of an atom emitting a photon. This indeterminacy is a consequence of our diagonal photon state vector being "represented" (transformed) into a linear superposition of vertical and horizontal photon state vectors. Thus the principle of superposition together with the projection postulate provides us with indeterminacy, statistics, and a way to "visualize" the collapse of a superposition of quantum states into one of the basis states. Problems in Quantum Physics
We have identified several problems in quantum physics that have new and plausible solutions when analyzed in terms of information.
The Connection to Information Philosophy
The Schrödinger equation that describes the time evolution of the wave function is linear, continuous, timereversible, and deterministic. It predicts probabilities for all possible locations, energy eigenvalues, and other observable quantities for a quantum system. But it does not predict or describe the socalled "collapse" of the wave function.
The "collapse" of the wave function actualizes one of those possibilities. Without the indeterministic "collapse" of the wave function, no new information could ever be created in the universe. In a universe described by a wave function that never collapses, nothing ever happens. The "collapse" is discontinuous, irreversible, and indeterministic, involving ontological chance, as first clearly seen by Albert Einstein in 1916. Ernest Rutherford saw that the time of radioactive nuclear decay is random in 1902, and he insightfully asked Niels Bohr in 1913 "How does the electron know which of your orbits to jump to?" Bohr could not say. But it was Einstein who first saw that the time and the directions of matter and light particles are fundamentally random when light and matter interact. He called it a "weakness in the theory."
Properly understanding quantum physics is thus central to understanding information philosophy. While this will present a challenge for some philosophers, especially those philosophers of science who have spent their careers challenging the standard interpretation of quantum mechanics, our goal is to provide vivid explanations of standard quantum mechanics, and the dozen or so problems above, with new illustrative diagrams and animations for the canonical experiments. In a deterministic world there is only one possible future. The information in such a world is constant (conserved like matter and energy). As Claude Shannon proved in his Theory of the Communication of Information, there must be alternative possibilities for new information to be generated. If there are two possibilities, an experiment (or a message) yields one bit of information. If four possibilities, two bits, etc. Since there is just one possible future in a deterministic universe, no new information is created. Many philosophers and physicists think that information is a conserved quantity. The Information Philosopher proposes to show that everything created since the origin of the universe over thirteen billion years ago has involved just two fundamental physical processes that combine to form the core of all creative processes. These two steps occur whenever even a single bit of new information is created and comes into the universe.
This twostep core creative process underlies the formation of microscopic objects like atoms and molecules, as well as macroscopic objects like galaxies, stars, and planets. With the emergence of teleonomic (purposive) information in selfreplicating systems, the same core process underlies all biological creation. But now some random changes in information structures are rejected by natural selection, while others reproduce successfully. Finally, with the emergence of selfaware organisms and the creation of extrabiological information stored in the environment, the same informationgenerating core process underlies communication, consciousness, free will, and creativity. The two physical processes in the creative process, quantum physics and thermodynamics, are somewhat daunting subjects for philosophers, and even for many scientists.
Quantum mechanics and thermodynamics are at the core of all creation
By creation we mean the emergence or coming into existence of recognizable information structures from a prior chaotic state in which there is no recognizable order or information.
Note there are three distinct kinds of information emergence:
By information we mean a quantity that can be understood mathematically and physically. It corresponds to the commonsense meaning of information, in the sense of communicating or informing. It also corresponds to the information stored in books and computers. But it also measures the information in any physical object, like a recipe, blueprint, or production process, and the information in biological systems, including the genetic code and the cell structures. Ultimately, the information we mean is the departure of a physical system from pure chaos, from "thermodynamic equilibrium." In equilibrium, there is only motion of the microscopic constituent particles ("the motion we call heat"). The existence of macroscopic structures, such as the stars and planets, and their motions, is a departure from thermodynamic equilibrium. Information is mathematically related to the measure of disorder known as the entropy by Ludwig Boltzmann's famous formula S = k log W, where S is the entropy and W is the probability  the number of ways (or microstates) that the internal components (the matter and energy particles of the system) can be rearranged and still be the same system (in a particular observable macrostate). The second law of thermodynamics says that the entropy (or disorder) of a closed physical system increases until it reaches a maximum, the state of thermodynamic equilibrium. It requires that the entropy of the universe is now and has always been increasing. This established fact of increasing entropy led many scientists and philosophers to assume that the universe we have is "running down" to a "heat death." They think that means the universe began in a very high state of information, since the second law requires that any organization or order is susceptible to decay. The information that remains today, in their view, has always been here. There is nothing new under the sun. But the universe is not a closed system. It is in a dynamic state of expansion that is moving away from thermodynamic equilibrium faster than entropic processes can keep up. The maximum possible entropy is increasing much faster than the actual increase in entropy. The difference between the maximum possible entropy and the actual entropy is potential information, as shown by David Layzer.
Creation of information structures means that in parts of the universe the local entropy is actually going down. Creation of a low entropy system is always accompanied by radiation of entropy away from the local structures to distant parts of the universe, into the night sky for example.
Information increases and we are cocreators of the universe
Creation of information structures means that today there is more information in the universe than at any earlier time. This fact of increasing information fits well with an undetermined universe that is still creating itself. In this universe, stars are still forming, biological systems are creating new species, and intelligent human beings are cocreators of the world we live in. All this creation is the result of the one core creative process. Understanding this process is as close as we are likely to come to understanding the idea of an anthropomorphic creator of the universe, a stillpresent divine providence, the cosmic source of everything good and evil. We will look next at the physics of quantum mechanics and thermodynamics in the creative process, then at information theory, on which we construct our information philosophy. For Teachers
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