Princeton, 16 February 1936

Mathematical preoccupations, 'the fools in Germany' and disdain for statistical physics.

Einstein excuses his long silence (the preceding letter dates from May 1933!) on the grounds that 'the mathematical imp sits unremittingly on my neck so that in spite of my white hair I scarcely have a quiet moment. And it is good that it is so; for human affairs in these times are less than cheerful, without speaking of the fools in Germany'. He does not however have serious fears for the future of Switzerland; as for America, he believes that they will 'find a path to the economic security of the individual before it is too late'; Americans are less constrained by tradition than Europeans, and more accustomed to instability of possessions and place in life.

Turning to scientific matters, he comments that 'I consider statistical physics, in spite of its success, to be merely a passing phase and I have some hope of achieving a really satisfactory theory of matter'. He outlines the equations for his current approach: 'Neutral and electrical particles appear as a hole in space, so that the metrical field folds back on itself. Space is represented as a double envelope [zweischalig]'. He is currently working on the problem of n bodies ('die Behandlung des Mehrkörperproblems') on this basis: 'We have already overcome the most serious difficulties of the problem, so that we shall soon see what there is to it. In any case it is a wonderful mathematical exercise'.

Although Einstein attributes his long silence to his deep immersion in work, his preoccupation at this time has been linked by some biographers with the painful decline of his wife Elsa, who died at the end of 1936 from heart and kidney problems.