EINSTEIN (ALBERT) Autograph letter signed ('A. Einstein') to G.Y. Rainich ('Sehr geehrter Herr Kollege!'), in German, thanking him for drawing his attention to his '...very fine and insightful paper...', going on to explain that he has been endeavouring '...to find a conception according to which the gravitational field and the electromagnetic field appear as components of one and the same mathematical construct, and in which the field equations likewise appear logically unified. This is evidently not the case...', illustrating his point with an equation, continuing with more explanation ('...it would be logically possible for 'matter' to be described by a formally different kind of field...'), and concluding '...This lack of internal completeness bothers me very much... I rather think that the Weyl-Eddington chain of reasoning will not lead to a real refinement of our world view...', one page, light dust-staining, creased at folds, small tear along horizontal fold, folio (282 x 223mm.), [n.p. but Berlin], 13 November [19]25 Footnotes: 'THIS METHOD CAN NEVER LEAD TO AN UNDERSTANDING OF THE DIFFERENCES BETWEEN THE ELECTRICALLY POSITIVELY AND NEGATIVELY CHARGED ELEMENTARY PARTICLES': EINSTEIN IN DISCUSSION WITH A FELLOW PHYSICIST AND COLLABORATOR. The recipient of our letter, the mathematical physicist George Yuri Rainich (1886-1968) was, at this time, professor of mathematics at Johns Hopkins University, whence he had fled after his arrest in Odessa in 1922. His research centered on general relativity and unified field theory and he had, the year before our letter, published the Rainich Conditions, which had arisen from the Einstein-Maxwell field equations. He had first encountered Einstein through Jerome Alexander, a colloid chemist, who had commissioned Rainich to translate Einstein's paper on critical opalescence into English, something which he not only did, but returned the paper bearing his own critical comments and amendments. According to his editors, Einstein's response is not extant. Einstein here writes in reply to Rainich's letter of 25 October in which he accused Einstein of not reading his paper [Transactions of the American Mathematical Society, January 1925] in which he explained 'I believe to have shown that within the framework of your original general theory of relativity a definite place is found for the electric quantities' and, somewhat audaciously (his words) supplying him with another copy of his paper (Collected Papers, no.96, p.116). In response '...Rather than engaging with Rainich's paper, he [Einstein] elaborated on how much it disturbed him that in the context of the 1915 Einstein equations with an electromagnetic source term, the electromagnetic and the gravitational field enter as separate entities...' (Collected Papers, Vol. 15, p.xliii). The correspondence continued, however, and the collaboration between Einstein and Rainich culminated in the important Einstein-Grommer paper of 1927, in which they '...aimed to derive the motion of particles subject to gravitational fields from the gravitational field equations themselves...' (Collected Papers, Vol.15, p.xxxix). Our letter is published in Diana Kormos Buchwald, ed., The Collected Papers of Albert Einstein, English Translation, 2018, Vol.15, no.106, pp.190-191. Provenance: Sotheby's New York, 6 December 1977, lot 11. This lot is subject to the following lot symbols: * * VAT on imported items at a preferential rate of 5% on Hammer Price and the prevailing rate on Buyer's Premium. For further information on this lot please visit Bonhams.com For further information about this lot please visit the lot listing