Philosophical Implications of Quantum Mechanics 207
compared with experiment, and it is quite unnecessary that any satisfying
description of the whole course of phenomena should be given.” This
controversy is being revisited today between the proponents and critics
of string theory. The critics say that string theory is not physics because
in its 30-year history it has never made a prediction that can be measured
or observed.
One should not interpret Dirac’s statement in a trivial way and
conclude that he and his colleagues decided that since their results
explain experimental results there was no need for further reflection.
The members of the Copenhagen school were just as perplexed and
disturbed by the new ideas. They, too, spent long hours trying hard to
understand the underlying ideas behind their new theory. The following
passage from Heisenberg’s book entitled Physics and Philosophy
indicates the nature of their frustration:
During the months following these discussions an intensive study of
all questions concerning the interpretation of quantum theory in
Copenhagen finally led to a complete and, as many physicists believed,
satisfactory clarification of the situation. But it is not a solution, which
one could easily accept. I remember discussions with Bohr which went
through many hours till very late at night and ended almost in despair;
and when, at the end of the discussion, I went alone for a walk in the
neighbouring park, I repeated to myself again and again the question:
Can nature possibly be as absurd as it seemed to us in those atomic
experiments?
Coming to grips with the peculiarities of quantum mechanics was no
easy task for Bohr and his co-workers. Einstein and his sympathizers in a
sense avoided the problem by refusing to give the new quantum
mechanics the status of a complete theory. They put the problem off by
claiming that some day a complete theory would arise and explain all.
Bohr, on the other hand, accepted the paradoxes of quantum mechanics
even though they contradicted the intuition of physics that he and others
had developed from their study of classical physics. Bohr recognized that
although quantum mechanics had completely invalidated classical
physics that it was still necessary to use the language of classical
mechanics to describe the behaviour of atomic systems. This is perhaps
the ultimate contradiction of quantum mechanics. It would be quite
impossible to develop quantum mechanics in purely quantum mechanical
terms. Thought by itself is a classical process. Our entire experience is
classical. If the laws of quantum physics operated on the macroscopic