3 2 6 D O C . 3 2 1 R E V I E W E L S B A C H
nature of space cannot be challenged. Nothing can be found out about reality by
mere conversion. Observation and experiment decide on reality.
4. The metric of real space cannot be determined by experiment because space
is not real.
How one responds to these theses depends on whether one grants reality to the
practically rigid body. If so, then the concept of distance corresponds to something
that can be experienced. Geometry then contains statements about possible exper-
iments; it is a physical science directly subject to experimental testing (standpoint
A). If no reality is conceded to the practically rigid measuring-body, then geometry
alone holds no statements about experiences (experiments), rather only geometry
together with the physical sciences (standpoint B). Physics has hitherto always
used the simpler standpoint A and largely owes to it its productivity; it uses it in all
its measurements. Seen from this standpoint, all the mentioned claims by Natorp
are incorrect; this surely does not need to be elaborated further in detail. If, howev-
er, one assumes standpoint B, which at the current state of science should be re-
garded as overly cautious, then geometry on its own is not experimentally testable.
Then geometrical measurements don’t exist at all. However, one does not have to
speak of the “ideality of space” as a result. “Ideality” is ascribable to all concepts;
this is no more and no less true with respect to space and time. Definite attribution
to sensory experiences is possible only for a complete scientific system of concepts.
In my view, Kant influenced developments unfavorably in that he granted a special
place to spatio-temporal concepts and their relations compared to other concepts.
Seen from standpoint B, though, the choice of geometric concepts and relations
is determined only by reasons of simplicity and practicality. Under no condition
does the choice of a non-Euclidean geometry presuppose Euclidean geometry as its
basis. But then nothing can be discerned empirically about the metric of space; not
because “space is not real,” but rather because with this choice of standpoint, ge-
ometry is not a complete physical system of concepts but only part of one.
Elsbach certainly does not agree with this way of arguing. Contrary to other rep-
resentatives of critical epistemology, he advocates the view that the latter could nei-
ther contradict a physical theory, nor anticipate one. In the last two chapters of the
book, which endorse Cassirer but in essential parts contain the author’s indepen-
dent arguments, criticism is directed against representatives of critical philosophy
who had earlier worked on the relation between philosophy and relativity
theory.[8]
On the basis of philosophical arguments, they arrived partly at a rejection of
relativity theory, partly at the result that the latter was merely an implementation of
Kantian thought. In both cases the error supposedly arose out of different usages of
words in philosophy and in physics. A philosopher calls space “absolute” in the
sense that the spatial concepts do not emerge logically out of observation; rather,
[col. 1691]
[col. 1692]