D O C U M E N T S 7 1 , 7 2 J U L Y 1 9 2 0 2 0 5
71. To Edouard Guillaume
[Berlin, 4 July 1920]
Dear Guillaume,
My behavior must appear unkind and unloyal to you; it may seem that I wanted
to condemn you by my
silence.[1]
In reality, though, it is entirely otherwise. I often
tried to understand your statements but always utterly failed. So if I wrote
Grossmann that it was nonsense, this must be understood with reference to me, or
better yet, to the present state of my brain;
nonsense[2]
is what one calls whatever
one cannot grasp; there is no other criterion. Now you must excuse me all the more,
since papers and manuscripts are raining down on poor me like whip lashes on a
cab
horse.[3]
But since you attack me so energetically, I have no choice but to try to
find elucidation through repeated correspondence on the basis of the enclosed little
notice[4]
and your letter.
You say, and were periods of clocks, hence things, not numbers, and
write[5]
.
Are these somehow symbolic equations? I cannot comprehend it as an equation be-
tween numbers. That is why I cannot understand all that follows and think that you
have temporarily fallen for a forbidden mysticism, in that you forgot that equations
deal with numbers. When I speak of “length l” or “period ” of a clock, then I
always mean “magnitude l of the length upon measurement with a given unit of
length” or “magnitude of the period upon measurement with a given standard
clock.”
I can think further only once you have removed this digestive complaint for me.
Warm greetings to you, our old colleagues, and your wife, from your old
Einstein.
72. From Joseph Petzoldt[1]
Spandau, 6 Wröhmänner St., 6 July 1920
Highly esteemed and dear Professor,
For a long time already, I have been cherishing the wish to be able to discuss the
epistemological aspect of relativity theory with you more often, which is especially
close to my heart. I just did not dare to express it because I was afraid of bothering
you, whose time is probably subject to high demands from very many quarters.
Now, however, the epistemological problems are becoming increasingly pressing
and need clarification more than ever. I could see this at the conference of the Kant
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