Einstein’s 1915 letter to Schlick on Hume, Kant, Mach,
and Special Relativity
It was recently (February 2019) reported in the press
that a hitherto unknown letter from Einstein to philosopher and physicist
Moritz Schlick had been discovered, wherein Einstein speaks of the influence of
Scottish philosopher David Hume
(1711–1776) upon his Theory of Special Relativity.
Professor David Purdie, at the University of Edinburgh, who discovered the letter was kind enough to send me a transcript of the German letter which is here presented in an English translation.
Professor David Purdie, at the University of Edinburgh, who discovered the letter was kind enough to send me a transcript of the German letter which is here presented in an English translation.
Though Hume and Mach’s influence on Einstein was
already known – e.g. as stated in Einstein’s Autobiographical Notes – this
letter is certainly revealing in other details.
Berlin, 14th December 1915.
Dear Colleague!
I received your paper yesterday and have already
thoroughly studied it through. It is one of the best that has ever been written
about relativity. From a philosophical point of view, nothing at all seems to
have been written that clearly about the subject. You have mastered the subject
matter so to expose it completely, I have nothing to do with your statements.
The relation of the theory of relativity to Lorentz’s theory is excellently
presented, truly masterfully in its relation to Kant’s teaching and his
successors. The trust in the “apodictic certainty” of the “synthetic judgments
a priori” is severely shaken by the realization of the invalidity of even one
of these judgments. Your remarks that positivism suggests Relativity Theory
without demanding it are also very correct. You have also correctly seen that
this line of thought had a great influence on my endeavours, namely E. Mach and
much more Hume, whose Treatise on the Understanding* I studied with zeal and
admiration shortly before finding the theory of relativity.
It is very possible that without these philosophical
studies I would not have come to the solution. Your remarks about the general
theory of relativity are also quite correct, as far as this theory has been
correct up to now.
The new finding is the result that there is a theory
which is compatible with all previous experiences, that the equations of
arbitrary transformations of space-time variables are covariant to each other.
Thus time & space lose the last rest of physical reality. All that remains
is to understand the world as a four-dimensional (hyperbolic) continuum of 4
dimensions. The fact that one can simplify the slides of the theory a posteriori
by choosing the reference system in such a way that the determinant equation
|guv| = -1 is fulfilled is of no significance in epistemological terms.
The empirical controllability of the theory is not
quite as sad as you indicate. The theory quantitatively explains the perihelion
movement of Mercury found by Leverrier.
The influence of the gravitational potential on the
colour of the emitted light demanded by the theory has already been
qualitatively confirmed by astronomy ([by] Freundlich). There is also a good
chance of testing the result concerning the curvature of the light rays by the
gravitational field. By asking you to visit me, if your way leads you to
Berlin, I wish you the best – regards your completely devoted,
A. Einstein
*[Einstein refers to “Traktat über den Verstand”,
which does not exist. Thus it is unclear whether Einstein is referring to
Hume’s Treatise on Human Nature (Ein Traktat Über Die Menschliche Natur) or An
Enquiry Concerning Human Understanding (Eine Untersuchung über den menschlichen
Verstand).]
[translated via DeepL Translator, then modified.]