When I take up a new book I always read its conclusions first. For I have discovered that even difficult books have conclusions that are easy to read and that give a first idea of their content. Of course, I expect my readers to do this also! Indeed, the present book offers them an opportunity for generalizing the method. After having gone over chapter 14 they should preferably look through chapters 5, 2, 13 and 10, or at least some of these (in this...