Berlin, 30 October 1931

On the unbridgeable divide between quantum mechanics and relativity: and some suggestions on macro-economics.

'The only thing that emerges from our research is the union of gravitation and electricity, whereby the equations of the latter are precisely the (relativistically formulated) Maxwell ones for empty space. In terms of the physics, there is therefore no progress there ... There is no density either of electricity or of mass in it; there the whole glorious construction fails; this already pertains to the problem of quanta, which until now is unattainable from the point of view of field theory (just as relativity is from the point of view of quantum mechanics)': Einstein provides some specific equations to give an idea of the approach.

Turning to economics, Einstein declares himself strongly against the gold standard, which he points out provides no real guarantee to the holder of paper money, and risks paralysing normal price mechanisms when there are local shortages of gold; he is also against a closed European market. He responds to specific questions from Besso on the macro-economic situation, particularly in relation to the economic crisis, his answers couched with a cheerful disclaimer: 'I reply by instinct and unencumbered by any real knowledge. But for that reason, no one need believe me.' The heart of the problem seems to be the vicious circle of unemployment and falling buying power, and the key solution lies in technical advances to increase productivity, whilst other measures should include the legal reduction of the duration of working life and a minimum wage. Einstein concludes by remarking that he plans to spend the winter in Switzerland as 'here things are beginning to be too hot for me [da es heir für mich brenzlig wird]' (a reference to the political turmoil which was to lead to the rise of the Nazi regime two years later).