1. A. Einstein, “The Foundations of General Relativity Theory,” in General Theory of Relativity,ed. C. W. Kilmister, Selected Readings in Physics (Oxford: Pergamon Press, 1973), pp. 141–172. The original paper appeared in Annalen der Physik 49 (1916): 769. On the ambiguity of Einstein’s statement of the Special Principle of Relativity, recall the discussion on pp. 25–27.
2. Ibid., p. 148.
3. See the very frank discussion by Hermann Bondi, “Is ‘General Relativity’ Necessary for Einstein’s Theory of Gravitation?” in Relativity, Quanta, and Cosmology in the Development of the Scientific Thought of Albert Einstein,ed. Francesco De Finis, 2 vols. (New York: Johnson Reprint Corp., 1979), pp. 179–186. According to Bondi, any notion of equivalence between inertial and accelerated observers is “physically meaningless,” which goes to show “how void of significance any general principle of relativity must be.” But because “a physically sound formulation of Einstein’s theory of gravitation exists not involving the physically empty concept of general relativity,” one may admire and embrace Einstein’s theory of gravitation while rejecting his route to it. “It is perhaps rather late to change the name of Einstein’s theory of gravitation, but general relativity is a physically meaningless phrase that can only be viewed as a historical memento of a curious philosophical observation.”
4. Einstein, “Foundations of General Relativity,” p. 143.
5. Ibid.