98 DOC. 21 GENERAL RELATIVITY
[p. 778] Plenary Session of November 4, 1915
On the General Theory of Relativity
My efforts in recent years were directed toward basing a general theory of relativity,
 also for nonuniform motion, upon the supposition of relativity. I believed indeed to
have found the only law of gravitation that complies with a reasonably formulated
postulate of general relativity; and I tried to demonstrate the truth of precisely this
solution in a paper1 that appeared last year in the Sitzungsberichte.
Renewed criticism showed to me that this truth is absolutely impossible to show
in the manner suggested. That this seemed to be the case was based upon a
misjudgment. The postulate of relativity-as far as I demanded it there-is always
satisfied if the Hamiltonian principle is chosen as a basis. But in reality, it provides
no tool to establish the Hamiltonian function H of the gravitational field. Indeed,
equation (77) l.c. which limits the choice of H says only that H has to be an invariant
toward linear transformations, a demand that has nothing to do with the relativity of
accelerations. Furthermore, the choice determined by equation (78) l.c. does not
 determine equation (77) in any way.
For these reasons I lost trust in the field equations I had derived, and instead
looked for a way to limit the possibilities in a natural manner. In this pursuit I arrived
at the demand of general covariance, a demand from which I parted, though with a
heavy heart, three years ago when I worked together with my friend Grossmann. As
a matter of fact, we were then quite close to that solution of the problem, which will
be given in the following.
Just as the special theory of relativity is based upon the postulate that all
equations have to be covariant relative to linear orthogonal transformations, so the
[p. 779] theory developed here rests upon the postulate of the covariance of all systems of
equations relative to transformations with the substitution determinant 1.
Nobody who really grasped it can escape from its charm, because it signifies a
real triumph of the general differential calculus as founded by Gauss, Riemann,
Christoffel, Ricci, and Levi-Civita.
1"Die formale Grundlage der Relativitätstheorie," Sitzungsberichte 41 (1914), pp.
 1066-1077. Equations of this paper are quoted in the following with the additional note
"l.c." in order to keep them distinct from those in the present paper.