The value of history lies not in the multitude of facts collected, but in their relation to each other, and in this respect an author can have no larger responsibility than any other scientific observer. If the sequence of events seems to indicate the existence of a law governing social development, such a law may be suggested, but to approve or disapprove of it would be as futile as to discuss the moral bearings of gravitation. Some years ago, when writing a sketch of the history of the colony of Massachusetts Bay, I became deeply interested in certain religious aspects of the Reformation, which seemed hardly reconcilable with the theories usually advanced to explain them. After the book had been published, I continued reading theology, and, step by step, was led back, through the schoolmen and the crusades, to the revival of the pilgrimage to Palestine, which followed upon the conversion of the Huns. As ferocious pagans, the Huns had long closed the road to Constantinople; but the change which swept over Europe after the year 1000, when Saint Stephen was crowned, was unmistakable; the West received an impulsion from the East. I thus became convinced that religious enthusiasm, which, by stimulating the pilgrimage, restored communication between the Bosphorus and the Rhine, was the power which produced the accelerated movement culminating in modern centralization. Meanwhile I thought I had discovered not only that faith, during the eleventh, twelfth, and early thirteenth centuries, spoke by preference through architecture, but also that in France and Syria, at least, a precise relation existed between the ecclesiastical and military systems of building, and that the one could not be understood without the other. In the commercial cities of the same epoch, on the contrary, the religious idea assumed no definite form of artistic expression, for the Gothic never flourished in Venice, Genoa, Pisa, or Florence, nor did any pure school of architecture thrive in the mercantile atmosphere. Furthermore, commerce from the outset seemed antagonistic to the imagination, for a universal decay of architecture set in throughout Europe after the great commercial expansion of the thirteenth century; and the inference I drew from these facts was, that the economic instinct must have chosen some other medium by which to express itself. My observations led me to suppose that the coinage might be such a medium, and I ultimately concluded that, if the development of a mercantile community is to be understood, it must be approached through its money...