This little book aims at showing a rather unfamiliar facet of medieval Europe's image: not cathedrals and castles, but, mainly, the walled cities and open country that were the stage of a commercial revolution between the tenth and the fourteenth centuries. Here, for the first time in history, an underdeveloped society succeeded in developing itself, mostly by its own efforts.

Such a statement could of course be challenged. It may be argued that men have been developing ever since they diverged from monkeys, or that the New Stone Age marked a steep acceleration as compared to the Old Stone Age, or that the ancient civilizations of Egypt, Mesopotamia, and China increased their production beyond comparison with their prehistoric predecessors. On the other hand, it may be observed that growth during the Commercial Revolution of the European Middle Ages was far slower than during the Industrial Revolution of the modern period, which in turn fell short of the breath-taking tempo of our own time.

All this is true, but economic development in each of its premedieval phases came to a full stop before the ceiling of what we would today call an underdeveloped society was broken. And if medieval growth was not fast, it was altogether irreversible; it created the indispensable material and moral conditions for a thousand years of virtually uninterrupted growth; and, in more than one way, it is still with us.