Chaos and symmetry in the history of mechanics

A practicing physicist can find inspiration and interesting ideas from looking at the original publications, even going back several centuries. The rate of progress in physics is slower than most modern scientists like to think; a fifty-year cycle in mechanics can be perceived simply by making a list of the most important books. A quick survey is presented to find out to what extent the early authors are aware of two modern concepts: symmetry as an argument to justify the basic mathematical relations and the chaotic behavior in their solutions. The personalities and philosophical inclinations of the writers come out very clearly. The origin of the variational principle and its meaning for Feynman's path integral are mentioned toward the end. © 1989 Società Italiana di Fisica.