xxvi INTRODUCTION TO VOLUME
2
preted entropy
as
probability.
If
the
Michelson-Morley
experiment
had
not
put
us
in the
most
awkward
position, no one
would have
accepted
the
theory
of
relativity
as a
(partial)
salvation.
Die
Relativitätstheorie ist
ebensowenig endgültig
befriedigend,
wie
es
z.
B. die klassische
Thermodynamik
war,
bevor Boltzmann die
Entropie
als Wahrscheinlichkeit
gedeutet
hatte. Wenn
uns
nicht das Michelson-
Morley'sche Experiment
in die
grösste Verlegenheit
gebracht hätte,
hätte niemand die Relativitätstheorie als eine
(halbe)
Erlösung emp-
funden.[58]
While
searching
for
adequate elementary
foundations
of
physics,
Einstein
continued
to
use
formal
principles as
tools to derive
new
connections
between
established
laws,
and
as
criteria
to
help
delimit the
possibilities
in the search
for
a
more
fundamental
theory.
In
1911
he stated this
strategy:
We
are
all
agreed
that the
quantum theory,
in its
present
form,
can
be
a
useful tool, but does
not
truly
constitute
a theory
in the
ordinary
sense
of
the word.
. . .
The
question
arises
of
knowing
what
are
the
general
principles
of
physics on
which
we
may rely
for the solution
of
the
prob-
lems that
concern
us.
Nous
sommes
tous
d'accord
que
la theorie des
quanta, sous sa
forme
actuelle,
peut etre
d'un
emploi
utile,
mais
ne
constitue
pas
veritablement
une
theorie
au sens
ordinaire du
mot.
. . .
La
question se pose
de savoir
quels
sont les
principes generaux
de la
Physique sur lequels nous
pouvons compter pour
la solution des
questions qui
nous
occupent.[59]
He
singled
out the
energy principle
and
Boltzmann's
principle as
such
principles;
elsewhere, he
similarly
utilized the
relativity principle
and the second law
of
thermodynamics.[60]
At
the end
of
the
decade Einstein believed that he had still
not
achieved
any
real
understanding
of
quantum phenomena.
His dissatisfaction
was
caused
by
the lack
of
an
interpretation
of Planck's
constant
"in
an
intuitive
manner"
("in anschau-
licher
Weise"),[61]
and
by
the role
of
the
quantum
of
electric
charge,
which
re-
mained
"an alien" ("ein
Fremdling")
in
Maxwell's
theory.[62]
He
was
convinced
that the
quantum
of
electricity
and
of
radiation should not
simply
be
postulated,
[58]
Einstein to
Arnold
Sommerfeld, 14
Janu-
ary
1908.
[59]
Solvay
1911,
p.
436.
[60] See, e.g.,
Einstein
1909c
(Doc. 60)
for
the
relativity principle,
and
Einstein 1912a for
the
laws
of
thermodynamics.
[61]
Einstein
to
Arnold
Sommerfeld,
14
Janu-
ary
1908.
[62]
Einstein
1909b
(Doc. 56), p.
192.