1 9 0 D O C U M E N T 5 1 J U N E 1 9 2 0
Perhaps the formulation of such questions is not so simple. But would it not be pos-
sible for you, guided by the above-mentioned consideration, to communicate
something of your own about a current aspect of modern relativity? A report on re-
cent researches—limited to some direction or a specific focus—would surely be
very warmly welcomed by everyone and would not cause you any substantial ef-
fort.
Weyl recently announced a talk “Electricity and Gravitation” and Laue also
wants to present something on
optics.[8]
So I ask you also for this reason to please
reconsider again whether you could not announce a talk. I would then request the
topic as soon as possible.– In the hope of not extending my request in vain, in view
of the good cause, I am with best regards, yours very truly,
A. Schoenflies.
51. From Moritz Schlick
Rostock, 23 Orléans St., 10 June 1920
Dear, highly esteemed Professor,
Yesterday your friendly letter
arrived.[1]
Thank you very much indeed for having
gone to such lengths with my
draft![2]
I only wish I had sent you the manuscript a
little earlier; then I could still have changed a few things. But it is too late now, be-
cause it has long since been typeset for the Naturwissenschaften: the issue con-
cerned is due tomorrow already, on the 11th. Please do not be irritated if I take up
your time again today with the old causality principle, returning once more to some
of the points. I would so much like to penetrate to the utmost clarity possible.
As concerns the possibility of causality in a world without uniformity, I fear I
left a gap in the explanation of my view and I hope that no difference of opinion
will remain after it has been filled. Surely, we could arrive at the discovery of
gravitation, e.g., by observing all comets that orbit the Sun along different hyper-
bolic
paths.[3]
But I would like to think that without a certain repetition of the same
in nature we would not even be in a position to describe the cometary course cor-
rectly nor to determine it quantitatively. To establish the various cometary loca-
tions, we evidently need certain instruments that can be set up the same way at
different times; we must be able to take measurements with them. And the practical
application of any scale and any dial seems to me to be based on the principle of
repeating physically equivalent processes. When we say that the various cometary
motions are based on the same law of gravity, then, it seems to me, the verifiable
sense[4]
of this statement can only be that the execution of very specific operations
on comet observations somehow leads to the same experiences. Such consider-