Hostname: page-component-59f8fd8595-gl4p7 Total loading time: 0 Render date: 2023-03-22T00:19:33.194Z Has data issue: true Feature Flags: { "useRatesEcommerce": false } hasContentIssue true

Why Quantize Gravity (or Any Other Field for That Matter)?

Published online by Cambridge University Press:  01 April 2022

Nick Huggett*
University of Illinois, Chicago
Craig Callender
University of California, San Diego
Send requests for reprints to Nick Huggett, Department of Philosophy, MC 267, University of Illinois at Chicago, Chicago, IL 60607–7114; email:


The quantum gravity program seeks a theory that handles quantum matter fields and gravity consistently. But is such a theory really required and must it involve quantizing the gravitational field? We give reasons for a positive answer to the first question, but dispute a widespread contention that it is inconsistent for the gravitational field to be classical while matter is quantum. In particular, we show how a popular argument (Eppley and Hannah 1997) falls short of a no-go theorem, and discuss possible counterexamples. Important issues in the foundations of physics are shown to bear crucially on all these considerations.

Quantum Gravity
Copyright © Philosophy of Science Association 2001

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)


Many thanks to John Baez, Jossi Berkovitz, Jeremy Butterfield, Tom Imbo, Michael Redhead, and Carlo Rovelli for discussions of these topics. The arguments of this paper are also discussed in Chapter 1 of Callender and Huggett 2001.


Aharonov, Yakir and Vaidman, Lev (1993), “Measurement of the Schrödinger Wave of a Single Particle”, Physics Letters A 178:3842.CrossRefGoogle Scholar
Belot, Gordon, Earman, John, and Ruetsche, Laura (1999), “The Hawking Information Loss Paradox: The Anatomy of a Controversy”, British Journal for the Philosophy of Science 50:189229.CrossRefGoogle Scholar
Bohr, Niels and Rosenfeld, Léon ([1933] 1983), “On the Question of the Measurability of Electromagnetic Field Quantities”, in Wheeler, John A. and Zurek, Wojciech H. (eds.), Quantum Theory and Measurement. Translated by Aage Petersen. Originally published as “Zur Frage der Messbarkeit der Elektromagnetischen Feldgrössen” (Mat.-fys. Medd Dan. Vid Selsk. 12). Princeton: Princeton University Press, 479522.Google Scholar
Brown, Harvey R. and Redhead, Michael L. G. (1981), “A Critique of the Disturbance Theory of Indeterminacy in Quantum Mechanics”, Foundations of Physics 11:120.CrossRefGoogle Scholar
Callender, Craig and Huggett, Nick (eds.) (2001), Physics Meets Philosophy at the Planck Length. Cambridge, UK: Cambridge University Press.Google Scholar
Ellis, John, Mavromatos, N. E., and Nanopoulos, D. V. (1999), “Search for Quantum Gravity”, gr-qc/9905048.CrossRefGoogle Scholar
Eppley, Kenneth and Hannah, Eric (1977), “The Necessity of Quantizing the Gravitational Field”, Foundations of Physics 7:5168.CrossRefGoogle Scholar
Feynman, Richard (1995), Feynman Lectures on Gravitation. Edited by Hatfield, Brian, Morinigo, Fernando B., and Wagner, William G.. Massachusetts: Addison-Wesley.Google Scholar
Ghirardi, GianCarlo, Rimini, Alberto, and Weber, Tullio (1986), “Unified Dynamics for Microscopic and Macroscopic Physics”, Physical Review D34:470491.Google Scholar
Jordan, Thomas F. (1975), “Why -i∇ is the Momentum”, American Journal of Physics 43:10891093.CrossRefGoogle Scholar
Maudlin, Tim (1994), Quantum Non-locality and Relativity. Oxford: Blackwell.Google Scholar
M⊘ller, C. (1962), “The Energy-Monentum Complex in General Relativity and Related Problems”, in Lichnerowicz, A. and Tonnelat, M. A. (eds.), Les Theories Relativistes de la Gravitation. Paris: Centre National de la Recherche Scientifique, 229.Google Scholar
Page, Don N. and Geilker, C. D. (1981), “Indirect Evidence for Quantum Gravity”, Physical Review Letters 47: 979.CrossRefGoogle Scholar
Pearle, Philip and Squires, Euan (1995), “Gravity, Energy Conservation and Parameter Values in Collapse Models”, quant-ph/9503019.Google Scholar
Peters, Achim, Chung, Keng Yeow, and Steven, Chu (1999), “Measurement of Gravitational Acceleration by Dropping Atoms”, Nature 400:849852.CrossRefGoogle Scholar
Rosenfeld, Léon (1963), “On the Quantization of Fields”, Nuclear Physics 40: 353.CrossRefGoogle Scholar
Unruh, William (1984), “Steps Towards a Quantum Theory of Gravity”, in Christensen, Steven M. (ed.), Quantum Theory of Gravity: Essays in Honor of the 60th Birthday of Bryce S. De Witt. Bristol: Hilger, 234242.Google Scholar
Wald, Robert (1994). Quantum Field Theory in Curved Spacetime and Black Hole Thermodynamics. Chicago: University of Chicago Press.Google Scholar