What happens to the single system remains it is true

of finite alterations experienced by part of the single systems.
What happens to the single system remains, it is true, entirely
unclarified by this mode of consideration; this enigmatic hap-
pening is entirely eliminated from the representation by the
statistical manner of Consideration.
But now I ask: Is there really any physicist who believes
that we shall never get any inside view of these important
alterations in the single systems, in their structure and their
causal connections, and this regardless of the fact that these
single happenings have been brought so close to us, thanks to
the marvelous inventions of the Wilson chamber and the
Geiger counter? To believe this is logically possible without
contradiction; but, it is so very contrary to my scientific
instinct that I cannot forego the search for a more complete
conception.
To these considerations we should add those of another
kind which also voice their plea against the idea that the
methods introduced by quantum mechanics are likely to give
a useful basis for the whole of physics. In the Schr6dinger
equation, absolute time, and also the potential energy, play
a decisive rSle, while these two concepts have been recognized
by the theory of relativity as inadmissable in principle. If
one wishes to escape from this difficulty he must found the
theory upon field and field laws instead of upon forces of
interaction. This leads us to transpose the statistical methods
of quantum mechanics to fields, that is to systems of infinitely
many degrees of freedom. Although the attempts so far
made are restricted to linear equations, which, as we know
from the results of the general theory of relativity, are insuf-
ficient, the complications met up to now by the very ingenious
attempts are already terrifying. They certainly will rise

378 AT~BERT EIXSTEIN. [J. F. I.
sky high if one wishes to obey the requirements of the general
theory of relativity, the justification of which in principle
nobody doubts.
To be sure, it has been pointed out that the introduction
of a space-time continuum may be considered as contrary to
nature in view of the molecular structure of everything which
happens on a small scale. It is maintained that perhaps the
success of the Heisenberg method points to a purely alge-
braical method of description of nature, that is to the elimina-
tion of continuous functions from physics. Then, however,
we must also give up, by principle, the space-time continuum.
It is not unimaginable that human ingenuity will some day
find methods which will make it possible to proceed along such
a path. At the present time, however, such a program looks
like an attempt to breathe in empty space.
There is no doubt that quantum mechanics has seized hold
of a beautiful element of truth, and that it will be a test stone
for any future theoretical basis, in that it must be deducible
as a limiting case from that basis, just as electrostatics is
deducible from the Maxwell equations of the electromagnetic
field or as thermodynamics is deducible from classical me-
chanics. However, I do not believe that quantum mechanics