D O C U M E N T 6 9 O C T O B E R 1 9 2 7 7 5 my opinion, if the errors committed are not rectified, generously and independently of the political views of those concerned, the already existing mistrust among the German people with regard to the state’s administration of justice will be disas- trously deepened. Respectfully yours, A. Einstein 69. From Pascual Jordan[1] [Göttingen?, between 11 October and 18 November 1927][2] Dear Professor Einstein, When, some time ago, I sent you my attempt to clarify the difficulties in the de- scription of radiation fluctuations using the new quantum mechanical methods, there were in your opinion two points that still remained unsatisfactory: namely, first, the zero-point energy and, second, the probabilities of extremely rare energy distributions (your formula ).[3] Concerning the first point, the zero- point energy, the situation is at present still not quite satisfactory. At any rate, we now have a rough sense of how we can get rid of this zero-point energy problem without relinquishing the advantages gained by the quantum theory of the radiation field. Some comments on this point will be made in the paper now in preparation by Pauli and me on the quantum theoretical formulation of electrodynamics in vacuum.[4] However, the second point seems to me to be definitively settled. Following the most recent articles by Dirac,[5] I have recently studied the correspondence be- tween a quantized wave field and a system of corpuscular quanta in some more detail.[6] On closer consideration, it is seen that there is such a complete internal equivalence between these two systems that one can assert: If one simply quantizes the oscillations of the radiation field without explicitly invoking the particle picture (as I did previously for a vibrating string),[7] then one arrives in all points at the same results as when the particle picture (in its exact quantum mechanical formu- lation, i.e., using symmetric[8] Schrödinger waves in an abstract, many-dimension- al coordinate space) is used. It can then be readily seen that every law that can be understood from the particle picture (such as in particular your formula )[9] is also a necessary result of the concept of quantized waves.[10] W v v 0 - E h = W v v 0 ---- - E h ------ =