WOLFGANG PAULI Exclusion principle and quantum mechanics Nobel Lecture december 13. 1946 The history of the discovery of the exclusion principle m, for which I have received the honor of the Nobel Prize award in the year 1945, goes back to my students days in Munich. While, in school in Vienna, I had already ob- tained some knowledge of classical physics and the then new Einstein rel- ativity theory, it was at the University of Munich that I was introduced by Sommerfeld to the structure of the atom- somewhat strange from the point of view of classical physics. I was not spared the which every physicist, accustomed to the classical way of thinking, experienced when he came to know of Bohrs u basic postulate of quantum theory m for the first time. At that time there were two approaches to the difficult problems con- nected with the quantum of action. One was an effort to bring abstract order to the new ideas by looking for a key to translate classical mechanics and electrodynamics into quantum language which would form a logical gen- eralization of these. This was the direction which was taken by Bohrs u correspondence principle > Sommerfeld, however, preferred, in view of the dificulties which blocked the use of the concepts of kinematical models, a direct interpretation, as independent of models as possible, of the laws of spectra in terms of integral numbers, following, as Kepler once did in his nvestigation of the planetary system, an inner feeling for harmony. Both methods, which did not appear to me irreconcilable, influenced me. The series of whole numbers 2, 8, 18, 32.. giving the lengths of the periods he natural system of chemical elements, was zealously discussed in Munich, ncluding the remark of the Swedish physicist, Rydberg, that these numbers are of the simple form 2 n, if n takes on all integer values. Sommerfeld tried especially to connect the number 8 and the number of corners of a cu A new phase of my scientific life began when I met Niels Bohr personally for the first time. This was in 1922, when he gave a series of guest lectures at Gottingen, in which he reported on his theoretical investigations on the Peri- odic System of Elements. I shall recall only briefly that the essential progress made by Bohrs considerations at that time was in explaining, by means of he spherically symmetric atomic model, the formation of the intermediateW OLFGANG P AUL I Exclusion principle and quantum mechanics Nobel Lecture, December 13, 1946 The history of the discovery of the « exclusion principle », for which I have received the honor of the Nobel Prize award in the year 1945, goes back to my students days in Munich. While, in school in Vienna, I had already ob￾tained some knowledge of classical physics and the then new Einstein rel￾ativity theory, it was at the University of Munich that I was introduced by Sommerfeld to the structure of the atom - somewhat strange from the point of view of classical physics. I was not spared the shock which every physicist, accustomed to the classical way of thinking, experienced when he came to know of Bohr’s « basic postulate of quantum theory » for the first time. At that time there were two approaches to the difficult problems con￾nected with the quantum of action. One was an effort to bring abstract order to the new ideas by looking for a key to translate classical mechanics and electrodynamics into quantum language which would form a logical gen￾eralization of these. This was the direction which was taken by Bohr’s « correspondence principle ». Sommerfeld, however, preferred, in view of the dificulties which blocked the use of the concepts of kinematical models, a direct interpretation, as independent of models as possible, of the laws of spectra in terms of integral numbers, following, as Kepler once did in his investigation of the planetary system, an inner feeling for harmony. Both methods, which did not appear to me irreconcilable, influenced me. The series of whole numbers 2, 8, 18, 32... giving the lengths of the periods in the natural system of chemical elements, was zealously discussed in Munich, including the remark of the Swedish physicist, Rydberg, that these numbers are of the simple form 2 n 2 , if n takes on all integer values. Sommerfeld tried especially to connect the number 8 and the number of corners of a cube. A new phase of my scientific life began when I met Niels Bohr personally for the first time. This was in 1922, when he gave a series of guest lectures at Göttingen, in which he reported on his theoretical investigations on the Peri￾odic System of Elements. I shall recall only briefly that the essential progress made by Bohr’s considerations at that time was in explaining, by means of the spherically symmetric atomic model, the formation of the intermediate