l x v i i i I N T R O D U C T I O N T O V O L U M E 1 6 field theory” (Doc. 260). It was an achievement he also wrote of proudly in a letter to Ehrenfest two days later (Doc. 259) and to Max von Laue a month later (Doc. 273). In a letter to Attilio Palatini on 12 May 1929, he noted yet again that only the solution of its problem of motion will determine whether the teleparallel approach is viable or not (Doc. 529). The new approach to unified field theory thus opened the possibility of finding solutions to long-standing problems, and work along these lines continued with in- tense phases of calculation and collaboration, partly done when Einstein withdrew from public life and spent extended periods of time in secluded residences in Scharbeutz and Gatow or, later, in Caputh. However, in mid-December 1928, dif- ficulties in working out the consequences of the new differential equations had piled up to such a point that Einstein reconsidered the basis of their derivation by means of Hamilton’s principle. On 13 December, he wrote to Müntz that he had a “simple, bold idea that will throw Hamilton’s principle overboard” (Doc. 334). In- stead of trying to recover the Maxwell equations in some acceptable limit, he would now “put the cart before the horse” and “choose the field equations in such a way that I can be certain that they will lead to the Maxwell equations” (Doc. 334). But yet again, things turned out to be more difficult, and for a few days in late De- cember he reverted to the “old Hamilton method once again” (Doc. 341). But over the New Year’s break, on another retreat in Gatow, Einstein gave up again on the variational approach and derived field equations based instead on some identities. On 27 December, he wrote to Müntz: “EUREKA!,” convinced that he had found a solution that was “so splendid, nothing nicer could be imagined” (Doc. 351). The new progress was written up in a brief paper, completed by 5 January 1929. Einstein was exhausted but happy about this new paper, “lying finished in front of me, compressed into seven pages under the title ‘Unified Field Theory’ ” (Doc. 358). To his son Eduard, he wrote on the same day that he was “very happy” because he had “more or less completed my life’s work” (Doc. 359). The paper was submitted on 10 January 1929 for publication in the Prussian Academy’s Proceed- ings (Einstein 1929n [Doc. 365]) and appeared under the somewhat less assertive title “On Unified Field Theory.” When published, the paper made a big splash in the press and received much public attention (Doc. 370). A press release appeared in the New York Times (Abs. 822) on 11 January, and reports followed on 12 January in the German and international press. The paper was reprinted in a record number of copies,[47] and Einstein wrote a popular exposition (Doc. 395), English translations of which ap-