2 8 0 D O C . 3 1 I D E A S A N D M E T H O D S
passage (see Hendrik A. Lorentz to Einstein, between 1 and 23 January 1915 [Vol. 8, Doc. 43], pp.
71-72), which may help to explain why Einstein expressed himself more carefully in subsequent writ-
ings (see Einstein to Hendrik A. Lorentz, 23 January 1915 [Vol. 8, Doc. 47], p. 83).
[14]The same formulation is used in Einstein 1910a (Vol. 3, Doc. 2), pp. 14–15.
[15]Einstein first explicitly identified the light postulate as the core of Lorentz’s theory based on an
immobile ether in Einstein 1911i (Vol. 3, Doc. 17), p. 6.
[16]In Einstein 1916c (Vol. 6, Doc. 29), Einstein discussed the central role of epistemological con-
siderations in the development of the theory of relativity and gave credit to Ernst Mach for their
formulation.
[17]See Einstein 1905r (Vol. 2, Doc. 23), sec. 1.
[18]At this point in the original text Einstein indicates a note he has appended at the foot of the page:
“Damit diese Definition widerspruchsfrei sei, ist folgendes nötig. Sind (α,β) und (α,γ) inbezug auf K
Paare gleichzeitiger Ereignisse, so sind auch β und γ gleichzeitig. Wäre dies nicht, so könnte man an
dem Prinzip der Konstanz der Lichtgeschwindigkeit nicht festhalten.”
[19]At this point in the original text Einstein indicates a note he has appended at the foot of the page:
“Die sub 1) und 2) benutzten Einheitsmassstäbe, seien—in relativer Ruhe miteinander verglichen—
einander gleich.— Es sei hier bemerkt, dass die Voraussetzung, dass diese Art Gleichheit (auch bei
Uhren), eine dauernde, von der Bewegungsvorgeschichte unabhängige sei, eine massgebende Voraus-
setzung der ganzen Theorie ist.” This last assumption is made explicit because it is dropped in the
unified theory of gravity and electromagnetism first presented in Weyl 1918b. In Einstein 1918g
(Doc. 8), Weyl’s theory is rejected for precisely this reason.
[20]Einstein first presented the derivation of the Lorentz transformation given here in Einstein
1907j (Vol. 2, Doc. 47), pp. 419–420.
[21]See Einstein 1921c (Doc. 52) for Einstein’s response to Poincaré’s conventionalism. For criti-
cisms of the theory of relativity by later conventionalists, see Hentschel 1990, pp. 293–336.
[22]The explicit formulation of assumption “c)” was prompted by Weyl’s theory (see note 19).
[23]Laue 1907.
[24]The heuristic value of the requirement of Lorentz invariance was first stated explicitly in Ein-
stein 1910a (Vol. 3, Doc. 2), p. 136.
[25]Einstein 1905s (Vol. 2, Doc. 24). See also Einstein 1909c (Vol. 2, Doc. 60), pp. 488–489, for a
concise version of the argument.
[26]Einstein’s signature at the bottom of [p. 15] is omitted.
[27]Minkowski 1908, 1909. Einstein first used Minkowski’s methods in a manuscript on special rel-
ativity of 1912–1914 (Vol. 4, Doc. 1). For historical discussions of Minkowski’s work, its origins, and
its reception, see, e.g., Corry 1997 and Walter, S. 1999.
[28]In eqs. (8) and (8a), “” should be “.”
[29]At this point in the original text Einstein indicates a note he has appended at the foot of the page:
“Man erkennt hieraus die fundamentale Bedeutung dieses Satzes für unsere Geometrie.”
[30]“ ” on the right side of the equation should be “ .”
[31]The analogy between the two types of transformation is fully exploited in the presentation of
special relativity in Einstein 1922c (Doc. 71).
[32]“ ” and “ ” in the next paragraph should be interchanged.
[33]The example was accordingly given pride of place in the introduction of Einstein 1905r (Vol.
2, Doc. 23).
[34]At this point in the original text Einstein indicates a note he has appended at the foot of the page:
“Die zu überwindende Schwierigkeit lag dann in der Konstanz der Vakuum-Lichtgeschwindigkeit,
die ich zunächst aufgeben zu müssen glaubte. Erst nach jahrelangem Tasten bemerkte ich, dass die
Schwierigkeit auf der Willkür der kinematischen Grundbegriffe beruhte.”
[35]Einstein 1907j (Vol. 2, Doc. 47).
[36]This is the first time that Einstein draws this analogy between what he identifies in this section
as considerations that played a leading role in the formulation of special and general relativity,
respectively.
[37]At this point in the original text Einstein indicates a note he has appended at the foot of the page:
“Bei der Überlegung ist natürlich vom Luftwiderstande abgesehen.”
[38]The equivalence hypothesis was first referred to by name in Einstein 1912c (Vol. 4, Doc. 3),
dx3′ dx3′2
dσ –dσ2