Einstein’s proof that charge-symmetric
solutions with the same mass are unavoidable, although to him a
rather negative feature of his unified field theories, later was
interpreted as Einstein’s discovery of the concept of antimatter
([357, 371
],
p. 78, footnote 44). To me, this seems to be a case of
whiggish historical hindsight. According to Bargmann, Einstein’s
lasting result is that he pointed out the importance of the discrete symmetry operations [8].