My association with Erwin Schrödinger was not a close one, although I spent the summer of 1927 in Zürich, with the stated purpose (stated in my letters to the John Simon Guggenheim Memorial Foundation) of working under his supervision. In fact, I spent most of my time in my room, trying to solve the Schrödinger equation for a system consisting of two helium atoms. I did not have very much success, except that, as was mentioned later by John C. Slater, I formulated a determinant of the several spin-orbital functions of the individual electrons as a way of ensuring that the wave function is antisymmetric. This was a device that Slater made much use of in discussing the electronic structure of atoms and also of molecules in 1929 and 1931.

Walter Heitler and Fritz London were also in Zürich that summer, also with the plan of working with Schrödinger. They told me that they had talked with Schrödinger several times about their work, while walking through the woods. I did not have even that much contact with him, because he was working so hard on his own problems.

It might be possible to put theoretical physicists on a scale ranging from one extreme, those who deal with ideas, to the other, those who deal with mathematics. Wolfgang Pauli is an example of a theoretical physicist near the mathematics end.