D O C U M E N T 4 7 3 F E B R U A R Y 1 9 2 7 4 6 5 Once this committee is established, unaffiliated with any political party, and solely according to the plan of justice, reason, and of endangered democratic prog- ress, it will decide itself what means will be suitable in achieving its lofty and just mission. We therefore ask first of all for a provisional agreement from each of those to whom we address this appeal. Romain Rolland, Henri Barbusse, A. Einstein 473. From Hermann Weyl Göttingen, Grüner Weg 3, 3 February 1927 Dear Colleague, Herglotz gave me the proofs of your note on the law of motion in the general theory of relativity.[1] I thank you very much for it, and also for the support you are thereby lending to my old idea about matter. However, I must confess that I did not understand what in it goes beyond my earlier developments. In my addendum to the paper by Bach[2] you quoted, Math. Zeitschr., vol. 13 (1922), pp. 134–145,[3] the [§1 of your note][4] is interpreted as the force on the body embedded in the gravitational field. Brief review of this in Raum, Zeit, Materie, 5th ed., p. 267.[5] The derivation of the equations of motion, without assumption about what hap- pens “inside” the material particle, is given by me ibid., §38 (p. 277) the § begins with the passage: “We now want to first of all derive the basic laws of mechanics without making use of the hypothetical laws in the interior of the elementary particles of matter.” I had already worked out this matter earlier, but not quite as carefully, in Ann. Phys. (“Field and Matter”) [6] and later a voluminous article by Mie appeared about it in Ann. Phys.[7] My method is somewhat different: I use the differential conservation laws in the form in which they are mathematical identities, independent of the field equations, and apply them to the interior of the matter tube, which I take as filled completely by an arbitrary fictitious field. In order, e.g., to obtain the concept of charge e with the conservation law , I fill the tube with arbitrary potentials continuously joined to the exterior, define [so yd ³ td de 0= ϕi fik ∂xi ∂ϕk ∂xk ∂ϕi, –= ∂xk ∂ f ik σi =