  This idea was seized upon by Herman [sic] Weyl. He said boldly that  the holes had to have the same mass as the electrons. Now Weyl was a  mathematician. He was not a physicist at all. He was just concerned  with the mathematical consequences of an idea, working out what can  be deduced from the various symmetries. And this mathematical  approach led directly to the conclusion that the holes would have to  have the same mass as the electrons. Weyl just published a blunt  statement that the holes must have the same mass as the electrons and did not make any comments on the physical implications of this  assertion. Perhaps he did not really care what the physical  implications were. He was just concerned with achieving consistent  mathematics.