Each of these classes reared its own children in its own fashion, and so naturally kept itself more or less continuously distinct from the others. General education was not organized in those ancient states, education was mainly a household matter (as it is still in many parts of India to-day), and so it was natural and necessary for the sons to follow in the footsteps of their father and to marry women accustomed to their own sort of household. Except during times of great political disturbance therefore, there would be a natural and continuous separation of classes; which would not, however, prevent exceptional individuals from intermarrying or passing from one class to another. Poor aristocrats would marry rich members of the mercantile class; ambitious herdsmen, artisans, or sailors would become rich merchants. So far as one can gather, that was the general state of affairs in both Egypt and Babylonia. The idea was formerly entertained that in Egypt there was a fixity of classes, but this appears to be a misconception due to a misreading of Herodotus. The only exclusive class in Egypt which did not intermarry was, as in England to-day, the semi-divine royal family. At various points in the social system there were probably developments of exclusiveness, an actual barring out of interlopers. Artisans of particular crafts possessing secrets, for example, have among all races and in all ages tended to develop guild organizations restricting the practice of their craft and the marriage of members outside their guild. Conquering people have also, and especially when there were marked physical differences of race, been disposed to keep themselves aloof from the conquered peoples, and have developed an aristocratic exclusiveness. Such organizations of restriction upon free intercourse have come and gone in great variety in the history of all long-standing civilizations. The natural boundaries of function were always there, but sometimes they have been drawn sharply and laid stress upon, and sometimes they have been made little of. There has been a general tendency among the Aryan peoples to distinguish noble (patrician) from common (plebeian) families; the traces of it are evident throughout the literature and life of Europe to-day, and it has received a picturesque enforcement in the “science” of heraldry. This tradition is still active even in democratic America. Germany, the most methodical of European countries, had in the Middle Ages a very clear conception of the fixity of such distinctions. Below the princes (who themselves constituted an exclusive class which did not marry beneath itself) there were the: (_a_) Knights, the military and official caste, with heraldic coats-of-arms; (_b_ and _c_) The Bürgerstand, the merchants, shipping people, and artisans; and (_d_) The Bauernstand, the cultivating serfs or peasants.