Simon Wolfe Saunders (born 30 August 1954) is a British philosopher of physics. He is noted for his work on

quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, q ...

(particularly the

many-worlds interpretation The many-worlds interpretation (MWI) is an interpretation of quantum mechanics that asserts that the universal wavefunction is objectively real, and that there is no wave function collapse. This implies that all possible outcomes of quantum ...

-the Everett interpretation), on identity and

indiscernibility The identity of indiscernibles is an ontological principle that states that there cannot be separate objects or entities that have all their properties in common. That is, entities ''x'' and ''y'' are identical if every predicate possessed by ''x ...

in physics, and on

structural realism Neorealism or structural realism is a theory of international relations that emphasizes the role of power politics in international relations, sees competition and conflict as enduring features and sees limited potential for cooperation. The anar ...

. Saunders is currently Professor of Philosophy of Physics at the

University of Oxford The University of Oxford is a collegiate research university in Oxford, England. There is evidence of teaching as early as 1096, making it the oldest university in the English-speaking world and the world's second-oldest university in contin ...

, and Fellow of

Merton College Merton College (in full: The House or College of Scholars of Merton in the University of Oxford) is one of the constituent colleges of the University of Oxford in England. Its foundation can be traced back to the 1260s when Walter de Merton, ...

, having moved to Oxford in 1996. He has previously held untenured posts at

Harvard University Harvard University is a private Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of high ...

(1990-1996), and temporary or visiting positions at

Wolfson College, Oxford Wolfson College () is a constituent college of the University of Oxford in England. Located in north Oxford along the River Cherwell, Wolfson is an all-graduate college with around sixty governing body fellows, in addition to both research an ...

(1985–89), the Hebrew University of Jerusalem (1989-1990), Harvard (2001),

École Polytechnique École may refer to: * an elementary school in the French educational stages normally followed by secondary education establishments (collège and lycée) * École (river), a tributary of the Seine The Seine ( , ) is a river in northern Franc ...

(2004),

University of British Columbia The University of British Columbia (UBC) is a public university, public research university with campuses near Vancouver and in Kelowna, British Columbia. Established in 1908, it is British Columbia's oldest university. The university ranks a ...

(2005),

Perimeter Institute Perimeter Institute for Theoretical Physics (PI, Perimeter, PITP) is an independent research centre in foundational theoretical physics located in Waterloo, Ontario, Canada. It was founded in 1999. The institute's founding and major benefactor i ...

(2005), and IMéRA (L’Institut Méditerranéen de Recherches Avancées) (2010). He is married to

Kalypso Nicolaïdis Kalypso Aude Nicolaïdis ( el, Καλυψώ Νικολαΐδη) is a Franco-Greek academic, currently Professor of International Relations and Director of the Center for International Studies at Oxford University, England. She teaches in the are ...

; they have two children.

Education

Saunders was an early graduate of the Physics and Philosophy undergraduate degree at the

. He then studied the part III Mathematics Tripos at

Christ's College, Cambridge Christ's College is a constituent college of the University of Cambridge. The college includes the Master, the Fellows of the College, and about 450 undergraduate and 170 graduate students. The college was founded by William Byngham in 1437 as ...

under

Martin Rees Martin John Rees, Baron Rees of Ludlow One or more of the preceding sentences incorporates text from the royalsociety.org website where: (born 23 June 1942) is a British cosmologist and astrophysicist. He is the fifteenth Astronomer Roya ...

John Polkinghorne John Charlton Polkinghorne (16 October 1930 – 9 March 2021) was an English theoretical physicist, theologian, and Anglican priest. A prominent and leading voice explaining the relationship between science and religion, he was professor of ...

, and Peter Goddard, and completed his PhD at

King's College, London King's College London (informally King's or KCL) is a public research university located in London, England. King's was established by royal charter in 1829 under the patronage of King George IV and the Duke of Wellington. In 1836, King' ...

in 1989 under the supervision of Michael Redhead. His thesis title was ‘Mathematical and Philosophical Foundations of Quantum Field Theory’.

Contributions to philosophy

Saunders was an early champion of 'structural realism', the view that mature physical theories correctly describe the structure of reality. Structural realism is today regarded by many philosophers as the most defensible form of realism. He was also amongst the first to draw attention to the consequences of

decoherence Quantum decoherence is the loss of Coherence (physics)#Quantum coherence, quantum coherence. In quantum mechanics, particles such as electrons are described by a wave function, a mathematical representation of the quantum state of a system; a p ...

for the many-worlds interpretation (MWI) of quantum mechanics; he defended a decoherence-based version of MWI in a series of articles throughout the 1990s. More recently, Saunders has worked extensively on the interpretation of probability in quantum mechanics. Along with

David Deutsch David Elieser Deutsch ( ; born 18 May 1953) is a British physicist at the University of Oxford. He is a Visiting Professor in the Department of Atomic and Laser Physics at the Centre for Quantum Computation (CQC) in the Clarendon Laboratory o ...

and David Wallace, he has developed techniques for deriving the

Born Rule The Born rule (also called Born's rule) is a key postulate of quantum mechanics which gives the probability that a measurement of a quantum system will yield a given result. In its simplest form, it states that the probability density of findi ...

, which relates quantum amplitudes to objective probabilities. He has applied these arguments to operational approaches to quantum mechanics as well as to MWI. In 2021 Saunders produced a branch counting derivation of the Born Rule. Saunders has also been a central figure in recent debates over identity and indiscernibility in physics. He was the first to apply the Hilbert-Bernays definition of identity in formal

first-order language First-order logic—also known as predicate logic, quantificational logic, and first-order predicate calculus—is a collection of formal systems used in mathematics, philosophy, linguistics, and computer science. First-order logic uses quantif ...

s to physical theories, both spacetime theories and quantum mechanics, going on to show that elementary

fermions In particle physics, a fermion is a particle that follows Fermi–Dirac statistics. Generally, it has a half-odd-integer spin: spin , spin , etc. In addition, these particles obey the Pauli exclusion principle. Fermions include all quarks and le ...

and composite

bosons In particle physics, a boson ( ) is a subatomic particle whose spin quantum number has an integer value (0,1,2 ...). Bosons form one of the two fundamental classes of subatomic particle, the other being fermions, which have odd half-integer sp ...

in quantum theory satisfied the principle of identity of indiscernibles, using the Hilbert-Bernays definition of identity. In related work, he has argued that classical particles could be treated as indistinguishable in exactly the same way that

quantum particle In quantum field theory, the energy that a particle has as a result of changes that it causes in its environment defines self-energy \Sigma, and represents the contribution to the particle's energy, or effective mass, due to interactions between ...

s (and that departures from classical statistics can be traced to discrete nature of the measure—

dimensionality In physics and mathematics, the dimension of a mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any point within it. Thus, a line has a dimension of one (1D) because only one coordi ...

—of subspace of

Hilbert space In mathematics, Hilbert spaces (named after David Hilbert) allow generalizing the methods of linear algebra and calculus from (finite-dimensional) Euclidean vector spaces to spaces that may be infinite-dimensional. Hilbert spaces arise natu ...

), and applied this to the

Gibbs paradox In statistical mechanics, a semi-classical derivation of entropy that does not take into account the indistinguishability of particles yields an expression for entropy which is not extensive (is not proportional to the amount of substance in qu ...

. Saunders has also developed a general framework for the treatment of

symmetries Symmetry (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definit ...

whereby all symmetries, not only gauge symmetries, as applied to strictly closed systems, yield only redescriptions of the same physical state of affairs. In a slogan: 'only invariant properties and relations are physically real'. In addition, Saunders has worked on quantum field theory, on the philosophy of time, and on the history of physics; he has written numerous encyclopaedia articles and book reviews.

Publications

Books

* ''Many Worlds?: Everett, quantum theory, and reality'', S. Saunders, J. Barrett, A. Kent, and D. Wallace (eds), Oxford: Oxford University Press. 2010. * ''The Philosophy of Vacuum'', S. Saunders and H. Brown (eds.),Clarendon Press, Oxford 1991.

Papers

* 2021 'Branch-counting in the Everett interpretation of quantum mechanics.', Proceedings of the Royal Society A, 477, 1-22 * 2010 ‘Chance in the Everett Interpretation’, in ''Many Worlds?: Everett, quantum theory, and reality'', S. Saunders, J. Barrett, A. Kent, and D. Wallace (eds), Oxford:

Oxford University Press Oxford University Press (OUP) is the university press of the University of Oxford. It is the largest university press in the world, and its printing history dates back to the 1480s. Having been officially granted the legal right to print book ...

(2010). * 2008b (with F.A. Muller), ‘Distinguishing Fermions’, British Journal of Philosophy of Science, 59, 499–548. * 2008a (with D. Wallace) ‘Branching and Uncertainty’, British Journal of Philosophy of Science, 59, 293–305. * 2007 ‘Mirroring as an A Priori Symmetry’, Philosophy of Science, 74, 452–480. * 2006a ‘On the Explanation of Quantum Statistics’, Studies in History and Philosophy of Modern Physics, 37, 192–211. Available online at https://arxiv.org/abs/quant-ph/0511136. * 2006b ‘Are Quantum Particles Objects?’, Analysis, 66, 52–63. * 2005a ‘Complementarity and Scientific Rationality’, ''

Foundations of Physics ''Foundations of Physics'' is a monthly journal "devoted to the conceptual bases and fundamental theories of modern physics and cosmology, emphasizing the logical, methodological, and philosophical premises of modern physical theories and procedur ...

'', 35, 347–72. Available online at https://arxiv.org/abs/quant-ph/0412195. * 2005b ‘What is Probability?’, in Quo Vadis Quantum Mechanics, A. Elitzur, S. Dolev, and N. Kolenda, eds., Springer. * 2004a ‘Derivation of the Born Rule from Operational Assumptions’, Proceedings of the Royal Society A, 460, 1–18. * 2003a: ‘Physics and Leibniz’s Principles’, in ''Symmetries in Physics: Philosophical Reflections'', K. Brading and E. Castellani, eds., Cambridge University Press. * 2003c ‘Structural Realism, Again’, ''Synthese'', 136, 127–33. * 2003d "Indiscernibles, General Covariance, and Other Symmetries: the Case for Non-reductive Relationalism", in ''Revisiting the Foundations of Relativistic Physics: Festschrift in Honour of John Stachel'', A. Ashtekar, D. Howard, J. Renn, S. Sarkar, and A. Shimony, (eds.), Kluwer. * 2002a ‘Is the Zero-Point Energy Real?’, in ''Ontological Aspects of Quantum Field Theory'', M. Kuhlmann, H. Lyre, and A. Wayne, (eds)., Singapore: World Scientific. * 2002b, ‘Why Relativity Contradicts Presentism’, ''Time, Reality, and Experience'', C. Callender, ed., Cambridge University Press, 2002. Reprinted in ''Time and Physics'': Volume 4 of ''The Philosophy of Time'', N. Oaklander, ed.,

Routledge Routledge () is a British multinational publisher. It was founded in 1836 by George Routledge, and specialises in providing academic books, journals and online resources in the fields of the humanities, behavioural science, education, law, ...

: forthcoming. * 2001a ‘Space-Time and Probability', in ''Chance in Physics: Foundations and Perspectives'', J. Bricmont, D. Dürr, M.C. Galavotti, G. Ghirardi, F. Petruccione, N. Zanghi (eds.),

Springer-Verlag Springer Science+Business Media, commonly known as Springer, is a German multinational publishing company of books, e-books and peer-reviewed journals in science, humanities, technical and medical (STM) publishing. Originally founded in 1842 ...

. * 2000 ‘Tense and Indeterminateness', ''Philosophy of Science (Proceedings)'', 67, S600-611. * 1999 ‘The "Beables" of Relativistic Pilot-Wave Theory', in ''From Physics to Philosophy'', J. Butterfield, and C. Pagonis, (eds.), Cambridge University Press. * 1998a ‘Hertz's Principles', in ''Heinrich Hertz: Classical Physicist, Modern Philosopher'', D. Baird et al, (eds.), Kluwer. * 1998b ‘Time, Quantum Mechanics, and Probability', ''Synthese'', 114, p.405-44. * 1996a ‘Time, Quantum Mechanics, and Tense', ''Synthese'', 107, 19-53. * 1996b ‘Naturalizing Metaphysics', ''

The Monist ''The Monist: An International Quarterly Journal of General Philosophical Inquiry'' is a quarterly peer-reviewed academic journal in the field of philosophy. It was established in October 1890 by American publisher Edward C. Hegeler. History Init ...

'', 80, p.44-69. * 1995a ‘Time, Quantum Mechanics, and Decoherence', ''Synthese'', 102, 235-66, 1995. * 1995b ‘Relativism', in ''Perspectives on Quantum Reality'', R. Clifton, ed., Kluwer, Dordrecht, 1995, p.125-42. * 1994a ‘A Dissolution of the Problem of Locality", ''Philosophy of Science (Proceedings)'', Vol.2, p. 88-98. * 1994b ‘Time and Quantum Mechanics', in ''Physics and the Now'', M. Bitbol, ed., Editions Frontieres, Paris, p. 21-70. * 1994c 'What is the Problem of Measurement', ''

Harvard Review of Philosophy ''The Harvard Review of Philosophy'' is an annual peer-reviewed academic journal of philosophy edited by a student collective at Harvard University.Scanlon, Thomas (2002) "Foreword" ''In'' Upham, S. Phineas, ''Philosophers in Conversation: Interv ...

'', Spring 1994. * 1994d ‘Decoherence and Evolutionary Adaptation', ''

Physics Letters A ''Physics Letters'' was a scientific journal published from 1962 to 1966, when it split in two series now published by Elsevier Elsevier () is a Dutch academic publishing company specializing in scientific, technical, and medical content. Its ...

'' 184, p. 1-5. * 1994e `Remarks on Decoherent Histories Theory and the Problem of Measurement', in ''Stochastic Evolution of Quantum States in Open Systems and in Measurement Processes'', L. Diosi, ed., p. 94-105,

World Scientific World Scientific Publishing is an academic publisher of scientific, technical, and medical books and journals headquartered in Singapore. The company was founded in 1981. It publishes about 600 books annually, along with 135 journals in various ...

, Singapore. * 1993a ‘Decoherence, Relative States, and Evolutionary Adaptation', ''Foundations of Physics'', 23, 1553–1585. * 1993b ‘To What Physics Corresponds', in Correspondence, Invariance, and Heuristics; ''Essays in Honour of Heinz Post'', S. French and H. Kaminga, (eds.), Kluwer, p. 295-326. * 1992 ‘Locality, Complex Numbers, and Relativistic Quantum Theory', ''Proceedings of the

Philosophy of Science Association The Philosophy of Science Association (PSA) is an international academic organization founded in 1933 that promotes research, teaching, and free discussion of issues in the philosophy of science from diverse standpoints. The PSA engages in activit ...

'', Vol.1, 1992, p. 365-380. * 1991 ‘The Negative Energy Sea', in 'Philosophy of Vacuum', S. Saunders and H. Brown (eds.),

Clarendon Press Oxford University Press (OUP) is the university press of the University of Oxford. It is the largest university press in the world, and its printing history dates back to the 1480s. Having been officially granted the legal right to print books ...

, 1991, p. 65-110. * 1991 ‘Reflections on Ether' (with H. Brown), in ''Philosophy of Vacuum'', p. 27-64. * 1988 ‘The Algebraic Approach to Quantum Field Theory', in ''Philosophical Foundations of Quantum Field Theory'', H. Brown and R. Harre (eds.), Clarendon Press.

References

External links

Homepage of Simon SaundersOxford philosophyLinacre College

The Everett interpretation website

The measurement problem in physics
''

In Our Time In Our Time may refer to: * ''In Our Time'' (1944 film), a film starring Ida Lupino and Paul Henreid * ''In Our Time'' (1982 film), a Taiwanese anthology film featuring director Edward Yang; considered the beginning of the "New Taiwan Cinema" * ''In ...

'',

BBC Radio 4 BBC Radio 4 is a British national radio station owned and operated by the BBC that replaced the BBC Home Service in 1967. It broadcasts a wide variety of Talk radio, spoken-word programmes, including news, drama, comedy, science and history fro ...

, a discussion with

Melvyn Bragg Melvyn Bragg, Baron Bragg, (born 6 October 1939), is an English broadcaster, author and parliamentarian. He is best known for his work with ITV as editor and presenter of '' The South Bank Show'' (1978–2010), and for the BBC Radio 4 documen ...

and guests

Basil Hiley Basil J. Hiley (born 1935), is a British quantum physicist and professor emeritus of the University of London. Long-time colleague of David Bohm, Hiley is known for his work with Bohm on implicate orders and for his work on algebraic descripti ...

, Simon Saunders and

Roger Penrose Sir Roger Penrose (born 8 August 1931) is an English mathematician, mathematical physicist, philosopher of science and Nobel Laureate in Physics. He is Emeritus Rouse Ball Professor of Mathematics in the University of Oxford, an emeritus f ...

, 5 March 2009 {{DEFAULTSORT:Saunders, Simon Wolfe 1954 births Living people Alumni of New College, Oxford Alumni of Christ's College, Cambridge Alumni of King's College London British physicists Fellows of Merton College, Oxford Fellows of Linacre College, Oxford Philosophers of physics