ABSTRACT
C R i T i c s of the Bohr-Heisenberg interpretation of quantum theory are, as a rule, dismissed as reactionaries who sigh for the good old days-the days of classical physics; the days when theories were not 'abstract' but could easily be visualized with the help of mechanical models; and the days of determinism. Hence I suppose I should repeat that I ardently admire new ideas, especially in physics, including ideas which have not been successful. Also, I am convinced that the 'abstract' character of a new theory is nothing against it, and that what strikes one generation of physicists as 'abstract' may no longer appear so to the next. (Many examples could be given to illustrate this.) And, as I must emphasize again, I am an indeterminist.1
