  "Symmetry" was one of the most important methodological themes in
20th-century physics and is probably going to play no lesser role in physics of
the 21st century. As used today, there are a variety of interpretations of this
term, which differ in meaning as well as their mathematical consequences.
Symmetries of crystals, for example, generally express a different kind of
invariance than gauge symmetries, though in specific situations the
distinctions may become quite subtle. I will review some of the various notions
of "symmetry" and highlight some of their uses in specific examples taken from
Pauli's scientific oevre.
