462 THE QUANTUM THEORYIt was a solitary position. Einstein knew that. Nor was he oblivious to other's
reactions. 'I have become an obstinate heretic in the eyes of my colleagues,' he
wrote to one friend [E6], and to another, 'I am generally regarded as a sort of
petrified object, rendered blind and deaf by the years. I find this role not too dis-
tasteful, as it corresponds very well with my temperament' [E7]. He knew, and
on occasion would even say, that his road was a lonely one [E8], yet he held fast.
'Momentary success carries more power of conviction for most people than reflec-
tions on principle' [E9].
Einstein was neither saintly nor humorless in defending his position on the
quantum theory. On occasion he could be acerbic. At one time, he said that Bohr
thought very clearly, wrote obscurely, and thought of himself as a prophet [SI].
Another time he referred to Bohr as a mystic [E10]. On the other hand, in a letter
to Bohr, Einstein referred to his own position by quoting an old rhyme: 'Uber die
Reden des Kandidaten Jobses/Allgemeines Schiitteln des Kopses' [Ell].*There
were moments of loneliness. 'I feel sure that you do not understand how I came
by my lonely ways' [El2]. He may not have expressed all his feelings on these
matters. But that was his way. 'The essential of the being of a man of my type
lies precisely in what he thinks and how he thinks, not in what he does or suffers'
[E3].
Einstein's apartness in regard to the foundations of quantum physics predates
the discovery of quantum mechanics. That is the second most important link
between the early and the later Einstein. I shall enlarge on this in Section 26c, but
first some final Comments on the subject of Chapter 2: Einstein's general attitude
toward the quantum and relativity theories.26b. Relativity Theory and Quantum Theory
It is a very striking characteristic of Einstein's early scientific writing that he left
relativity theory separate from quantum theory, even on occasions where it would
have been natural and straightforward to connect them. This separation is already
evident in his very first paper on special relativity, in which he noted, 'It is remark-
able that the energy and frequency of a light complex vary with the state of motion
of the observer according to the same law' [E13]. Here was an obvious opportu-
nity to refer to the relation E = hv of his paper on light-quanta, finished only a
few months earlier. But Einstein did not do that. Also, in the September 1905
paper on relativity [El4], he referred to radiation but not to light-quanta. In his
1909 address at Salzburg, Einstein discussed his ideas both on relativity theory
and on quantum theory but kept these two areas well separated [El 5]. As we saw
in Section 21c, in his 1917 paper Einstein ascribed to light-quanta an energy E
= hv and a momentum p = hv/c. This paper concludes with the remark,
'Energy and momentum are most intimately related; therefore, a theory can be
*Roughly: There was a general shaking of heads concerning the words of candidate Jobs.