It seems that this has only now come to light; and, in my opinion, the fact has been quite correctly analysed in Rosenkranz's preface to the second volume of his complete edition of Kant's works. We must, however, remember that many scholars, being unceasingly occupied as teachers and authors, find very little time left for private and exact research. It is certain that docendo disco (I learn by teaching) is not unconditionally true; sometimes indeed one is tempted to parody it by saying: semper docendo nihil disco (by always teaching I learn nothing); and even what Diderot puts into the mouth of Rameau's nephew is not altogether without reason: “'And as for these teachers, do you suppose they understand the sciences they give instruction in? Not a bit of it, my dear sir, not a bit of it.