The golden jubilee of the Dutch Physical Society in April 1971 was concluded with a lecture by Samuel Goudsmit on the history of the discovery of the electron spin. Actually, his could hardly be called a polished lecture; it was a grandiose artistic performance, full of wit and emotional involvement. Goudsmit, then at the end of his scientific career, gave a very personal account of how chance and the guidance by Ehrenfest, their far-sighted supervisor, led him and Uhlenbeck to formulate their remarkable discovery. When, in connection with the present book [*], the question turned up how to discuss the early history of electron spin, my thoughts returned to that day, nearly twenty five years ago, when I had been impressed by Goudsmit's truly humane wisdom. After weighing various alternatives I thought: why not let the master speak for himself? Thus I came to translate Goudsmit's historic lecture. Its text was not meant to be published as a paper, but Goudsmit subsequently consented to its publication from a tape recording [1]. Apart from a few minor changes I have tried to present Goudsmit's very personal style by giving a literal translation of the words spoken in Dutch. A number of references to the papers mentioned by Goudsmit have been added.