 Both Whitehead and I were disappointed that Principia Mathematica was only viewed from a philosophical standpoint. People were interested in what was said about the contradictions and in the question whether ordinary mathematics had been validly deduced from purely logical premisses, but they were not interested in the mathematical techniques developed in the course of the work.…Even those who were working on exactly the same subjects did not think it worth while to find out what Principia Mathematica had to say on them. I will give two illustrations: Mathematische Annalen published about ten years after the publication of Principia a long article giving some of the results which (unknown to the author) we had worked out in Part IV of our book. This article fell into certain inaccuracies which we had avoided, but contained nothing valid which we had not already published. The author was obviously totally unaware that he had been anticipated. The second example occurred when I was a colleague of Reichenbach at the University of California. He told me that he had invented an extension of mathematical induction which he called ‘transfinite induction’. I told him that this subject was fully treated in the third volume of the Principia. When I saw him a week later, he told me that he had verified this. (1959: 86)