How to Save the Symmetry Principle

Abstract

The symmetry principle is a central tenet of science studies, but clear statements of the principle are hard to find. A standard formulation is that true and false beliefs should be explained in the same way. This claim is multiply and harmfully ambiguous. The aim of this paper is to identify the main ambiguities and defend a more precise version of the symmetry principle. I argue that the principle should refer to types of cause not causes in general, that the relevant types are rational and irrational causes not social and non-social ones, that true and false beliefs should be explained impartially not identically, and that impartiality does not imply a ban on truth as an explanation of belief. The symmetry principle that emerges from these choices is that historians should not assume in advance of historical inquiry that true beliefs are best explained rationally and that false beliefs are best explained irrationally. I argue that this principle does what all symmetry principles should do: it is conducive to good historical writing, protects us from a genuine threat, makes room for the sociology of true beliefs, does not cast doubt on legitimate projects such as internal history of science, and does not commit us to controversial philosophical positions such as skepticism about present-day scientific theories.