Author's comments: The following article appeared in novembre, 2007 in the popular scientific review, Pour la Science, but in a version slightly revised by the editors and their consultants for expository purposes and with diagrams added. I am sure the revised form is indeed easier for a layman to understand, but some assessments were added that are not mine. Rather than interfere with the editors' difficult task of turning arcane material into something meaningful to their readers, I let the revised version stand.
Robert P. Langlands
Author's comments: This review comes with a supplement (footnote) that contains the comments of several leading specialists and will be much more useful to the potential reader of the book, whether a novice or a specialist, than the review itself.
Author's comments: The article is an exercise in the reading of mathematics from earlier times. An explanation of Descartes's solution of the problem of Pappus as included in the appendix "La géométrie" to "Discours de la méthode" and an explanation of a solution to another form of the same problem by Fermat, described briefly in a letter included in his collected works, are taken as an occasion to compare the mathematical styles of the two men and to observe their mutual debt to Apollonius as well as the differences in their depth of understanding of his work.
Author's comments: The following brief discourse was delivered in Erlangen in October, 2004, on the occasion of the award of the Karl Georg Christian von Staudt-Preis to Günter Harder. It does not do justice to his many contributions to mathematics, but does attempt to express my great admiration of him and my great respect for the passion and the tenacity with which he continues to reflect on what seem to me some of the central problems of the modern theory of numbers.
Author's comments: This note contains a few recollections of a year I spent in Turkey in 1967/68, where my office was adjacent to that of Cahit Arf, known, among other things, for the Hasse-Arf theorem and the Arf invariant. It was he who referred me -- as I was first attempting to define local \(\epsilon\)-factors for Artin \(L\)-functions -- to the paper of Hasse published in the Acta Salmanticensia. Hasse's paper was my first introduction to the methods that had already been introduced for calculating and comparing the \(\epsilon\)-factors.