Philosophical perspectives on ad hoc hypotheses and the Higgs mechanism


We examine physicists’ charge of ad hocness against the Higgs mechanism in the standard model of elementary particle physics. We argue that even though this charge never rested on a clear-cut and well-entrenched definition of “ad hoc”, it is based on conceptual and methodological assumptions and principles that are well-founded elements of the scientific practice of high-energy particle physics. We further evaluate the implications of the recent discovery of a Higgs-like particle at the CERN’s Large Hadron Collider for the charge of ad hocness against the Higgs mechanism.

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  1. 1.

    On July 4, 2012, ATLAS and CMS, the two largest experimental collaborations at CERN, announced the observation of a new particle whose properties, as measured up to now, agree well with those of a Higgs boson to be expected from the SMHM; see (ATLAS Collaboration 2012) and (CMS Collaboration 2012). Meanwhile, more data have been collected and analyzed, and the “observation” has been upgraded to a “discovery”; see (ATLAS Collaboration 2013) and (CMS Collaboration 2013).

  2. 2.

    This characterization of the SMHM in terms of spontaneous symmetry breaking and a degenerate ground state has to be taken with a grain of salt and is in some respects misleading; see (Smeenk 2006; Healey 2007, Chapt. 6.5; Friederich 2013) for clarifications aimed at philosophers.

  3. 3.

    These considerations are enforced by noting that from a gauge-independent perspective, local gauge symmetry is never broken and the Higgs field, as a gauge-dependent variable, has zero expectation value under all conditions. See (Elitzur 1975) for an important result on this matter and (Friederich 2013, Sects. 5, 6) for a more detailed discussion of the ramifications of this and other results that is aimed at philosophers.

  4. 4.

    Even though the values of parameters used in the SMHM are theoretically unconstrained and therefore arbitrary, they appear by no means random. For example, the so-called CKM matrix which relates the three quark generations in the SM, is approximately diagonal, even though its elements are not in any way determined by the theory and could therefore be arbitrary. Other oddities are the enormous spread of the charged-fermion masses, spanning six orders of magnitude, with the largest one (the top-quark mass) being suspiciously close to the Higgs field’s vacuum expectation value.

  5. 5.

    See (Karaca 2010), Chapter 6, for a more detailed overview of philosophical accounts of ad hoc hypotheses.

  6. 6.

    The fact that the neutrino and the trans-Uranian planet hypotheses were independently “confirmed” in the past and, as a result of this, no charge of “ad hocness” is raised against them any more seems to vindicate the general consensus on ad hoc hypotheses indicated by Leplin’s condition of justification.

  7. 7.

    In Sect. 5, “A world without the Higgs mechanism”, of Quigg (2007), Chris Quigg offers more detailed considerations as to what a world described by the SM0 would be like.

  8. 8.

    In 1979 S. Glashow shared the Nobel prize with S. Weinberg and A. Salam “for their contributions to the theory of the unified weak and electromagnetic interactions between elementary particles” (

  9. 9.

    See (Karaca 2010), Chapter 7, for the original statement of the claim that the SMHM is not strictly speaking ad hoc on any account according to which ad hocness requires that a conflict be removed between an established theory and incoming empirical data. Rather, Karaca argues that the SMHM is an ad hoc hypothesis that was proposed to solve a conceptual problem, namely, the problem of how to account for the non-zero masses of vector bosons while preserving the gauge invariance of the theory.

  10. 10.

    Whether Weinberg himself considered his theory a modification of Glashow’s seems difficult to decide. His only reference to Glashow’s model is in a footnote, where he characterizes it as “similar to [his own model]; the chief difference is that Glashow introduces symmetry-breaking terms into the Lagrangian, and therefore gets less definite predictions.” (Weinberg 1967, p. 1266)

  11. 11.

    The failure of renormalizability in Glashow’s theory may have been the chief reason why it was not recognized earlier as an important contribution. According to the Science Citation Index (Glashow 1961) was cited only once per year between 1961 and 1967. In fact, even Weinberg’s paper was cited less than five times in the three years between its publication and ’t Hooft’s proof of renormalizability (’t Hooft 1971). For a historical comparison of Glashow’s and Weinberg’s theories, see (Karaca 2013).

  12. 12.

    To arrive at the SM from the starting point of the SM0 is conceptually more straightforward than to arrive at the SM from the starting point of Glashow’s theory, which, however, is closer to the actual historical course of events. Thus, whether one prefers to conceive of the SM as an ad hoc modification of Glashow’s theory or of the SM0 depends, respectively, on whether one prefers a historical perspective or one of rational reconstruction. (We would like to thank an anonymous referee for proposing this distinction.)

  13. 13.

    The latest results can be accessed from the following URLs (retrieved on February 17, 2014) for the ATLAS and CMS experiments, respectively:;

  14. 14.

    The idea alluded to here is that considerations involving the string theory landscape may help dispelling the naturalness problem by integrating the SM in a multiverse scenario, where anthropic arguments may be used to explain away the perceived fine tuning of fundamental parameters as an unproblematic observation-selection effect. See (Donoghue 2007) for details.


  1. ATLAS Collaboration. (2012). Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC. Physics Letters B, 716, 1–29.

  2. ATLAS Collaboration. (2013). Evidence for the spin-0 nature of the Higgs boson using ATLAS data. Physics Letters B, 726, 120–144.

  3. Callaway, D. J. E. (1988). Triviality pursuit: Can elementary scalar particles exist? Physics Reports, 167, 241–320.

    Article  Google Scholar 

  4. Cho, A. (2007). Physicists’ nightmare scenario: The Higgs and nothing else. Science, 315, 1657–1658.

    Article  Google Scholar 

  5. CMS Collaboration. (2012). Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC. Physics Letters B, 716, 30–61.

  6. CMS Collaboration. (2013). Properties of the observed Higgs-like resonance using the diphoton channel. CERN report number: CMS-PAS-HIG-13-016.

  7. Donoghue, J. F. (2007). The fine-tuning problems of particle physics and anthropic mechanisms. In B. Carr (Ed.), Universe or multiverse (pp. 231–246). Cambridge: Cambridge University Press.

    Google Scholar 

  8. Elitzur, S. (1975). Impossibility of spontaneously breaking local symmetries. Physical Review D, 12, 3978–3982.

    Article  Google Scholar 

  9. Farhi, E., & Jackiw, R. (1982). Dynamical gauge symmetry breaking; a collection of reprints. Singapore: World Scientific.

    Google Scholar 

  10. Feng, J. L. (2013) Naturalness and the status of supersymmetry. Forthcoming in annual review of nuclear and particle science.

  11. Friederich, S. (2013). Gauge symmetry breaking in gauge theories—In search of clarification. European Journal for Philosophy of Science, 3, 157–182.

  12. Giudice, G. F. (2010). A zeptospace odyssey—A journey into the physics of the LHC. New York: Oxford University Press.

    Google Scholar 

  13. Glashow, S. L. (1961). Partial-symmetries of weak interactions. Nuclear Physics, 22, 579–588.

  14. Grünbaum, A. (1976). Ad hoc auxiliary hypotheses and falsificationism. British Journal for the Philosophy of Science, 27, 329–362.

    Article  Google Scholar 

  15. Healey, R. (2007). Gauging what’s real: The conceptual foundations of contemporary gauge theories. Oxford: Oxford University Press.

    Google Scholar 

  16. Hunt, J. C. (2012). On ad hoc hypotheses. Philosophy of Science, 79, 1–14.

    Article  Google Scholar 

  17. Jackiw, R. (1998). Field theory: Why have some physicists abandoned it? Proceedings of the National Academy of Sciences USA, 95, 12776–12778.

    Article  Google Scholar 

  18. Karaca, K. (2010). Historical and conceptual foundations of the higher dimensional unification program in physics. Dissertation, submitted in May 2010 at Indiana University.

  19. Karaca, K. (2013). The construction of the Higgs mechanism and the emergence of the electroweak theory. Studies in History and Philosophy of Modern Physics, 44, 1–16.

    Article  Google Scholar 

  20. Krämer, M. (2013). “The landscape of new physics”, blog entry. Retrieved on February 17, 2014, from

  21. Leplin, J. (1975). The concept of an ad hoc hypothesis. Studies in History and Philosophy of Science, 5, 309–345.

    Article  Google Scholar 

  22. LEP Working Group for Higgs Boson Searches. (2003). Search for the standard model Higgs boson at LEP. Physics Letters B, 565, 61–75.

  23. LHC Higgs Cross Section Working Group Collaboration. (2011). Handbook of LHC Higgs cross sections: 1. Inclusive observables.

  24. Moriyasu, K. (1983). An elementary primer for gauge theory. Singapore: World Scientific.

    Google Scholar 

  25. Morrison, M. (2003). Spontaneous symmetry breaking: theoretical arguments and philosophical problems. In K. Brading & E. Castellani (Eds.), Symmetries in physics: Philosophical reflections (pp. 347–363). Cambridge: Cambridge University Press.

    Google Scholar 

  26. Peskin, M. E. (2012). Theoretical summary lecture for Higgs hunting 2012. SLAC-PUB-15224.

  27. Popper, K. (1959). The logic of scientific discovery. London: Hutchinson.

    Google Scholar 

  28. Popper, K. (1974). Replies to my critics. In P. A. Schilpp (Ed.), The philosophy of Karl Popper (pp. 961–1197). Library of Living Philosophers, Open Court, La Salle.

  29. Quigg, C. (2007). Spontaneous symmetry breaking as a basis of particle mass. Reports on Progress in Physics, 70, 1019–1053.

  30. Ross, D. A., & Veltman, M. (1975). Neutral currents and the Higgs mechanism. Nuclear Physics B, 95, 135–147.

    Article  Google Scholar 

  31. Schaffner, K. F. (1974). Einstein versus Lorentz: Research programmes and the logic of comparative theory evaluation. The British Journal for the Philosophy of Science, 25, 45–78.

    Article  Google Scholar 

  32. Schumm, B. A. (2004). Deep down things: The breathtaking beauty of particle physics. Baltimore, Maryland: John Hopkins University Press.

    Google Scholar 

  33. Slavnov, A. A. (1979). Application of path integrals to non-perturbative study of massive Yang-Mills theory. In S. Albeverio, Ph. Combe, R. Høegh-Krohn, G. Rideau, M. Siruge-Collin, M. Siruge, & R. Stora (Eds.), Feynman path integrals (pp. 289–303). Lecture Notes in Physics 106, Springer, Berlin.

  34. Smeenk, C. (2006). The elusive Higgs mechanism. Philosophy of Science, 73, 487–499.

  35. Smolin, L. (1997). The life of the cosmos. Oxford: Oxford University Press.

    Google Scholar 

  36. Susskind, L. (1979). Dynamics of spontaneous symmetry breaking in the Weinberg-Salam theory. Physical Review D, 20, 2619–2625.

    Article  Google Scholar 

  37. ‘t Hooft, G. (1971). Renormalizable Lagrangians for massive Yang-Mills fields. Nuclear Physics B, 35, 167–188.

    Article  Google Scholar 

  38. Weinberg, S. (1967). A model of leptons. Physical Review Letters, 19, 1264–1266.

    Article  Google Scholar 

  39. Wetterich, C. (2012). Where to look for solving the gauge hierarchy problem? Physics Letters B, 718, 573–576.

    Article  Google Scholar 

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This research is part of the project “An Ontological and Epistemological Analysis of the Higgs-mechanism,” funded by the Deutsche Forschungsgemeinschaft (DFG, contract HA 2990/4-1), within the research collaboration “The Epistemology of the Large Hadron Collider (LHC)” at the University of Wuppertal: The authors would like to thank two anonymous referees, as well as audiences at conferences and seminars in Ankara, Dresden, Tel Aviv and Wuppertal, for thoughtful comments and suggestions.

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Correspondence to Koray Karaca.

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Friederich, S., Harlander, R. & Karaca, K. Philosophical perspectives on ad hoc hypotheses and the Higgs mechanism. Synthese 191, 3897–3917 (2014).

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  • Ad hoc hypothesis
  • Higgs mechanism
  • Particle physics
  • Spontaneous symmetry braking
  • Fine-tuning
  • Naturalness