[History of] origins of physical models

Considering the reputation of physics as an empirical science, it is remarkable how many significant theories were in fact first constructed on largely aesthetic grounds. Notable examples include Maxwell's equations for electromagnetism (1880s), general relativity (1915), the Dirac equation for relativistic electrons (1928), and QCD (early 1970s). This history makes it seem more plausible that one might be able to come up with an ultimate model of physics on largely aesthetic grounds, rather than mainly by working from detailed experimental observations.