EINSTEIN'S RESPONSE TO THE NEW DYNAMICS 443
and spoke in this sense of a "Gespensterfeld"', ghost field [B2], clearly a reference
to Einstein's idea of a Tuhrungsfeld.' Shortly thereafter, Born wrote to Einstein:
My idea to consider Schroedinger's wavefield as a 'Gespensterfeld' in your sense
of the word proves to be more useful all the time.... The probability field
propagates, of course, not in ordinary space but in phase space (or configuration
space). [B3]*Once more, but now for the last time, we encounter Einstein as a transitional
figure in the period of the birth of quantum mechanics.
Bern's papers had a mixed initial reception. Several leading physicists found it
hard if not impossible to swallow the abandonment of causality in the classical
sense, among them Schroedinger. More than once, Bohr mentioned to me that
Schroedinger told him he might not have published his papers had he been able
to foresee what consequences they would unleash.** Einstein's position in the
years to follow can be summarized succinctly by saying that he took exception to
every single statement in Bern's papers and in the letter Born subsequently wrote
to him. His earliest expressions of lasting dissent I know of date from December
1926 and are, in fact, contained in his reply to one of Bern's letters: 'Quantum
mechanics is very impressive. But an inner voice tells me that it is not yet the real
thing. The theory produces a good deal but hardly brings us closer to the secret
of the Old One. I am at all events convinced that He does not play dice. Waves
in 3 n-dimensional space whose velocity is regulated by potential energy (e.g., rub-
ber bands) ...' [Ell].
'Einstein's verdict... came as a hard blow' to Born [B4]. There are other
instances as well in which Einstein's reactions were experienced with a sense of
loss, of being abandoned in battle by a venerated leader. Thus Goudsmit told me
of a conversation that took place in mid-1927 (to the best of his recollection [Gl])
between Ehrenfest and himself. In tears, Ehrenfest said that he had to make a
choice between Bohr's and Einstein's position and that he could not but agree with
Bohr. Needless to say, Einstein's reactions affected the older generation more
intensely than the younger.
Of the many important events in 1927, four are particularly significant for the
present account.
February 1927. In a lecture given in Berlin, Einstein is reported to have said
that 'what nature demands from us is not a quantum theory or a wave theory;
rather, nature demands from us a synthesis of these two views which thus far has
exceeded the mental powers of physicists' [El2]. At this point in the developments,
as others are about to take over, it should be recalled one more time that as early
"This important letter is not included in the published Born-Einstein correspondence. I thank John
Stachel for drawing my attention to its existence.
** Schroedinger retained reservations on the interpretation of quantum mechanics for the rest of his
life [SI].