This latter change in the economic conditions of the world exercised its most powerful effect, however, on the character of the mediaeval town, which had remained substantially unchanged since the first great expansion at the end of the thirteenth and the beginning of the fourteenth centuries. With the extension of commerce and the opening up of communications, there began that evolution of the town whose ultimate outcome was to entirely change the central idea on which the urban organization was based. The first requisite for a town, according to modern notions, is facility of communication with the rest of the world by means of railways, telegraphs, postal system, and the like. So far has this gone now that in a new country, for instance, America, the railway, telegraph lines, etc., are made first, and the towns are then strung upon them, like beads upon a cord. In the mediaeval town, on the contrary, communication was quite a secondary matter, and more of a luxury than a necessity. Each town was really a self-sufficing entity, both materially and intellectually. The modern idea of a town is that of a mere local aggregate of individuals, each pursuing a trade or calling with a view to the world-market at large. Their own locality or town is no more to them economically than any other part of the world-market, and very little more in any other respect. The mediaeval idea of a town, on the contrary, was that of an organization of groups into one organic whole. Just as the village community was a somewhat extended family organization, so was, _mutatis mutandis_, the larger unit, the township or city. Each member of the town organization owed allegiance and distinct duties primarily to his guild, or immediate social group, and through this to the larger social group which constituted the civic society. Consequently, every townsman felt a kind of _esprit de corps_ with his fellow-citizens, akin to that, say, which is alleged of the soldiers of the old French "foreign legion" who, being brothers-in-arms, were brothers also in all other relations. But if every citizen owed duty and allegiance to the town in its corporate capacity, the town no less owed protection and assistance, in every department of life, to its individual members.