Weyl explicitly stated in correspondence with Einstein that mathematics, not physics, was the driving force behind his unified field theory.

With the advent of the quantum theory of the electron around 1927/28 Weyl abandoned his gauge theory of 1918. He did so because in the new quantum theory a different kind of gauge invariance associated with Dirac’s theory of the electron was discovered which, as had been suggested by Fock (1926) and London (1927), more adequately accounted for the conservation of electric charge.[92] Why did Weyl hold on to his gauge theory for almost a decade despite a preponderance of compelling empiric