  It was also during the first years of the 1920s that Weyl came to  appreciate the power and utility of group theory, initially in  connection with his work on the solution to the Riemann-Helmholtz-Lie problem of space. Weyl analyzed this problem, the  Raumproblem, in a series of articles and lectures during the period 1921–23. Weyl (1949b, 400) noted that his interest in  the philosophical foundations of the general theory of relativity had motivated his analysis of the representations and invariants of the  continuous groups: