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Core Concepts

Best Explanation
Divided Line
Downward Causation
Emergent Dualism
Identity Theory
Infinite Regress
Mental Causation
Multiple Realizability
Schrödinger's Cat


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
Isaiah Berlin
Bernard Berofsky
Robert Bishop
Susanne Bobzien
Emil du Bois-Reymond
Hilary Bok
Laurence BonJour
George Boole
Émile Boutroux
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
Carl Ginet
Edmund Gettier
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
Andrea Lavazza
Keith Lehrer
Gottfried Leibniz
Michael Levin
George Henry Lewes
David Lewis
Peter Lipton
John Locke
Michael Lockwood
E. Jonathan Lowe
John R. Lucas
James Martineau
Storrs McCall
Hugh McCann
Colin McGinn
Michael McKenna
Brian McLaughlin
Paul E. Meehl
Uwe Meixner
Alfred Mele
John Stuart Mill
Dickinson Miller
C. Lloyd Morgan
Thomas Nagel
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
Thomas Reid
Charles Renouvier
Nicholas Rescher
Richard Rorty
Josiah Royce
Bertrand Russell
Paul Russell
Gilbert Ryle
Kenneth Sayre
Moritz Schlick
Arthur Schopenhauer
John Searle
Wilfrid Sellars
Henry Sidgwick
Walter Sinnott-Armstrong
Saul Smilansky
Michael Smith
L. Susan Stebbing
George F. Stout
Galen Strawson
Peter Strawson
Eleonore Stump
Richard Taylor
Kevin Timpe
Mark Twain
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
Ludwig Wittgenstein
Susan Wolf


Michael Arbib
Bernard Baars
John S. Bell
Charles Bennett
Ludwig von Bertalanffy
Susan Blackmore
Margaret Boden
David Bohm
Niels Bohr
Ludwig Boltzmann
Emile Borel
Max Born
Walther Bothe
Hans Briegel
Leon Brillouin
Stephen Brush
Henry Thomas Buckle
Donald Campbell
Anthony Cashmore
Eric Chaisson
Jean-Pierre Changeux
Arthur Holly Compton
John Conway
John Cramer
E. H. Culverwell
Charles Darwin
Terrence Deacon
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
Michael Gazzaniga
GianCarlo Ghirardi
Nicolas Gisin
Paul Glimcher
Thomas Gold
Brian Goodwin
Joshua Greene
Jacques Hadamard
Stuart Hameroff
Patrick Haggard
Augustin Hamon
Sam Harris
Martin Heisenberg
Werner Heisenberg
Jesper Hoffmeyer
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
Hendrik Lorentz
Josef Loschmidt
Ernst Mach
Henry Margenau
James Clerk Maxwell
Ernst Mayr
Ulrich Mohrhoff
Jacques Monod
Emmy Noether
Howard Pattee
Wolfgang Pauli
Massimo Pauri
Roger Penrose
Steven Pinker
Max Planck
Susan Pockett
Henri Poincaré
Daniel Pollen
Ilya Prigogine
Hans Primas
Adolphe Quételet
Jerome Rothstein
David Ruelle
Erwin Schrödinger
Aaron Schurger
Claude Shannon
Herbert Simon
Dean Keith Simonton
B. F. Skinner
Roger Sperry
Henry Stapp
Tom Stonier
Antoine Suarez
Leo Szilard
William Thomson (Kelvin)
Peter Tse
John von Neumann
John B. Watson
Daniel Wegner
Steven Weinberg
Paul A. Weiss
Norbert Wiener
Eugene Wigner
E. O. Wilson
H. Dieter Zeh
Ernst Zermelo
Wojciech Zurek


Mental Causation
James Symposium

Infinite Regress
Plato in the Theatetus (200D-201C) defined knowledge as justified true belief. Justification was providing some reasons (λόγος or συλλογισμῶ), a rational explanation for the belief. True opinion accompanied by reason is knowledge. (δόξαν ἀληθῆ μετὰ λόγου ἐπιστήμην εἶναι) (202C)

Although "justified true belief" is the traditional philosophical definition of knowledge, still in use in modern positions on epistemology, the ancients were already skeptical of this Platonic idea. Socratic dialogues normally did not reach any positive conclusions; they were "negative dialectics."

Indeed, the Theaetetus ends with Socrates' utter rejection of perception, true belief, or true belief combined with reasons or explanations as justification. Socrates says:

And it is utterly silly, when we are looking for a definition of knowledge, to say that it is right opinion with knowledge, whether of difference or of anything else whatsoever. So neither perception, Theaetetus, nor true opinion, nor reason or explanation combined with true opinion could be knowledge (epistéme).

καὶ παντάπασί γε εὔηθες, ζητούντων ἡμῶν ἐπιστήμην, δόξαν φάναι ὀρθὴν εἶναι μετ᾽ ἐπιστήμης εἴτε διαφορότητος εἴτε ὁτουοῦν. οὔτε ἄρα αἴσθησις, ὦ Θεαίτητε, οὔτε δόξα ἀληθὴς οὔτε μετ᾽ ἀληθοῦς δόξης λόγος προσγιγνόμενος ἐπιστήμη ἂν εἴη.

An infinite regress arises when we ask what are the justifications for the reasons themselves.

If the reasons count as knowledge, they must themselves be justified with reasons for the reasons, and so on, ad infinitum.

The problem of the infinite regress was a critical argument of the Skeptics in ancient philosophy.

Sextus Empiricus tells us there are two basic Pyrrhonian modes or tropes that lead the skeptic to suspension of judgment (ἐποχῆ):

They [skeptics] hand down also two other modes leading to suspension of judgement. Since every object of apprehension seems to be apprehended either through itself or through another object, by showing that nothing is apprehended either through itself or through another thing, they introduce doubt, as they suppose, about everything. That nothing is apprehended through itself is plain, they say, from the controversy which exists amongst the physicists regarding, I imagine, all things, both sensibles and intelligibles; which controversy admits of no settlement because we can neither employ a sensible nor an intelligible criterion, since every criterion we may adopt is controverted and therefore discredited.

And the reason why they do not allow that anything is apprehended through something else is this: If that through which an object is apprehended must always itself be apprehended through some other thing, one is involved in a process of circular reasoning or in regress ad infinitum. And if, on the other hand, one should choose to assume that the thing through which another object is apprehended is itself apprehended through itself, this is refuted by the fact that, for the reasons already stated, nothing is apprehended through itself. But as to how what conflicts with itself can possibly be apprehended either through itself or through some other thing we remain in doubt, so long as the criterion of truth or of apprehension is not apparent, and signs, even apart from demonstration, are rejected.
(Outlines of Pyrrhonism, Loeb Library, R.G.Bury tr., 1.178-79)

The skeptic can always ask a philosopher for justifying reasons. When those reasons are given, he can demand their justification, and this in turn leads to an infinite regress of justifications.

The endless controversy and disagreement of all philosophers cautions us against accepting any of their arguments as knowledge.

Second only to Kant 's "scandal" that philosophers cannot logically prove the existence of the external world, it is scandalous that professional philosophers to this day are in such profound disagreement about what it means to know something.

Epistemologists may not all be wrong, but with their conflicting theories of knowledge, how many of them are likely to be right?

This is especially dismaying for those epistemologists who still see a normative role for philosophy that could provide an a priori foundation for scientific or empirical a posteriori knowledge. Kant called this the synthetic a priori.

In recent years, professional epistemologists have been reduced to quibbling over "Gettier problems" - clever sophistical examples and counterexamples that defeat the reasoned justifications for true beliefs.

Following some unpublished work of Gregory O'Hair, David Armstrong identifies and diagrams several possible ways to escape the Skeptic's infinite regress, including:

  • Skepticism - knowledge is impossible

  • The regress is infinite but virtuous

  • The regress is finite, but has no end
    (Coherence view)

  • The regress ends in self-evident truths, the axioms of geometry, for example
    (Foundationalist view)

  • Non-inferential credibility, such as direct sense perceptions

  • Externalist theories (O'Hair is the source of the term "externalist")

  • Causal view (Ramsey)

  • Reliability view (Ramsey)
For Teachers
For Scholars

Chapter 3.7 - The Ergod Chapter 4.2 - The History of the Knowledge Problem
Part Three - Value Part Five - Problems
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