Caste in its later developments is so complex and irregular, that it is impossible to summarize it in a formula or explain it as the development of one principle. In the earliest form known two principles are already in operation. We have first racial distinction. The three upper castes represent the invading Aryans, the fourth the races whom they found in India. In the modern system of caste, race is not a strong factor. Many who claim to be Brahmans and Kshatriyas have no Aryan blood, but still the Aryan element is strongest in the highest castes and decreases as we descend the social scale and also decreases in the higher castes in proportion as we move from the north-west to the east and south. But secondly in the three upper castes the dividing principle, as reported in the earliest accounts, is not race but occupation. We find in most Aryan countries a division into nobles and people, but in India these two classes become three, the priests having been able to assume a prominence unknown elsewhere and to stamp on literature their claim to the highest rank. This claim was probably never admitted in practice so completely as the priests desired. It was certainly disputed in Buddhist times and I have myself heard a young Rajput say that the Brahmans falsified the Epics so as to give themselves the first place. It is not necessary for our purpose to describe the details of the modern caste system. Its effect on Indian religion has been considerable, for it created the social atmosphere in which the various beliefs grew up and it has furnished the Brahmans with the means of establishing their authority. But many religious reformers preached that in religion caste does not exist--that there is neither Jew nor Gentile in the language of another creed--and though the application of this theory is never complete, the imperfection is the result not of religious opposition but of social pressure. Hindu life is permeated by the instinct that society must be divided into communities having some common interest and refusing to intermarry or eat with other communities. The long list of modern castes hardly bears even a theoretical relation to the four classes of Vedic times.[423] Numerous subdivisions with exclusive rules as to intermarriage and eating have arisen among the Brahmans and the strength of this fissiparous instinct is seen among the Mohammedans who nominally have no caste but yet are divided into groups with much the same restrictions.