In January 1925, when Kronig was a still a Columbia University PhD student, he first proposed electron spin after hearing Pauli in Tübingen. Werner Heisenberg and Wolfgang Pauli immediately hated the idea. They had just ruled out all imaginable actions from quantum mechanics. Now Kronig was proposing to set the electron rotating in space. Pauli especially ridiculed the idea of spin, saying that "it is indeed very clever but of course has nothing to do with reality". Faced with such criticism, Kronig decided not to publish his theory and the idea of electron spin had to wait for others to take the credit. Ralph Kronig had come up with the idea of electron spin several months before Uhlenbeck and Goudsmit. Most textbooks credit these two Dutch physicists with the discovery.