Published online by Cambridge University Press: 01 January 2022
This paper aims at answering the simple question, “What is spontaneous symmetry breaking (SSB) in classical systems?” I attempt to do this by analyzing from a philosophical perspective a simple classical model which exhibits some of the main features of SSB. Related questions include: What does it mean to say that a symmetry is spontaneously broken? Is it broken without any causes, or is the symmetry not broken but merely hidden? Is the principle, “no asymmetry in, no asymmetry out,” violated by SSB? What really distinguishes SSB from the usual types of symmetry breaking?
I would like to thank Gérard Emch for comments on an earlier draft of this paper. I would also like to thank Jeremy Butterfield, Craig Callender, Nick Huggett, John Stachel, and Sang Wook Yi for questions and comments at the PSA 2002 session at which I read a short version of this paper.