“Every history is a map: it leaves out some features of reality, and singles out others which are thought to display its essential structure. When a historical map is drawn, as ours is, from specific groups outward, it has a special character. The process of mapping becomes the surveyor's process of triangulation, and the reference points are important less in themselves than as marks for triangulation-that is, as points from which to take a bearing. This is the principle which has guided us whenever we have had to make a choice between men; which of them, we have asked, best expresses the essence of his time.”