When mathematical enquiry in the previous century succeeded in eliminating the concept of the infinitely small from infinitesimal analysis, this was regarded as a great advance in the sense of the postulate of purity in mathematical method.¹ For the prince of mathematicians, Gauss, no doubt under the influence of Kant's critique of reason, had rejected this concept as unmathematical, and most other creative mathematicians of the time could not ignore the fact that the infinitely small was a quite unwanted guest in the well defined domain of mathematical knowledge.