Thus an equality of knowledge, advantage, and interests united the priests against the Kshatriyas, Vaiçyas, and Çudras. By the consciousness that they were in possession of the means to win the favour of the gods for the king, the nobles, and the people, the pious feeling aroused among them was greatly assisted towards gaining the recognition of the other orders. Like the Kshatriyas, they must have scorned to descend to the occupations of the Vaiçyas; they must have felt that only the priest born a priest could perform the priestly service, or offer pleasing sacrifice to the gods. They must have maintained that birth alone in the order could confer the capacity for so important and lofty a calling as theirs. If nobles and priests debarred the Vaiçyas from entrance into their order, their occupations, and modes of life, they must have been no less careful to maintain the advantages of their birth against the Çudras. If the separation of the orders was the result of a natural progress, if the effort of the favoured classes to close their circles was essentially promoted by the common contrast of the immigrants to the remnant of the old population, the natural conditions in which the Aryas were placed on the Ganges were not without an influence on the maintenance of the separation when once introduced. In the land of the Indus the Aryas had not learned to endure such a climate and such heat as they found on the Ganges. The atmosphere began by degrees to undermine the active and vigorous feeling of the Aryas, to lead them to a life of greater calm and rest, which inclined them to retain the conditions and circumstances once introduced. The orders attain complete exclusiveness and become castes when not only the change from one to another is forbidden, but when even marriage between the members of different orders is either impossible, or if allowed entails the loss of order, and other disadvantages. We do not exactly know to what extent the mutual exclusiveness of the Kshatriyas, the Brahmans, and the Vaiçyas was carried; we only know that these distinctions existed, and that marriages between the orders took place at the time when the priests succeeded in wresting the first place on the throne and in the state from the Kshatriyas, who had maintained it for centuries.