Abstract
The elucidation of the gauge principle ‘‘is the most pressing problem in current philosophy of
physics’’ said Michael Redhead in 2003. This paper argues for two points that contribute to this
elucidation in the context of Yang–Mills theories. (1) Yang–Mills theories, including quantum
electrodynamics, form a class. They should be interpreted together. To focus on electrodynamics is
potentially misleading. (2) The essential role of gauge and BRST symmetries is to provide a local field
theory that can be quantized and would be equivalent to the quantization of the non-local reduced
theory. If this is correct, the gauge symmetry is significant, not so much because it implies ontological
consequences, but because it allows us to quantize theories that we would not be able to quantize
otherwise. Thus, in the context of Yang–Mills theories, it is essentially a pragmatic principle. This
does not seem to be the case for the gauge symmetry in general relativity.