India is a land of paradox. Possessing a fundamental geographical unity, India has never known real political union save that recently imposed externally by the British "Raj." Full of warlike stocks, India has never been able to repel invaders. Occupied by many races, these races have never really fused, but have remained distinct and mutually hostile, sundered by barriers of blood, speech, culture, and creed. Thus India, large and populous as Europe or China, has neither, like China, evolved a generalized national unity; nor, like Europe, has developed a specialized national diversity; but has remained an amorphous, unstable indeterminate, with tendencies in both directions which were never carried to their logical conclusion. India's history has been influenced mainly by three great invasions: the Aryan invasion, commencing about 1500 B.C.; the Mohammedan invasion, extending roughly from A.D. 1000 to 1700, and the English invasion, beginning about A.D. 1750 and culminating a century later in a complete conquest which has lasted to the present day. The Aryans were a fair-skinned people, unquestionably of the same general stock as ourselves. Pressing down from Central Asia through those north-western passes where alone land-access is possible to India, elsewhere impregnably guarded by the mountain wall of the Himalayas, the Aryans subdued the dark-skinned Dravidian aborigines, and settled down as masters. This conquest was, however, superficial and partial. The bulk of the Aryans remained in the north-west, the more adventurous spirits scattering thinly over the rest of the vast peninsula. Even in the north large areas of hill-country and jungle remained in the exclusive possession of the aborigines, while very few Aryans ever penetrated the south. Over most of India, therefore, the Aryans were merely a small ruling class superimposed upon a much more numerous subject population. Fearing to be swallowed up in the Dravidian ocean, the Aryans attempted to preserve their political ascendancy and racial purity by the institution of "caste," which has ever since remained the basis of Indian social life. Caste was originally a "colour line." But it was enforced not so much by civil law as by religion. Society was divided into three castes: Brahmins, or priests; Kshatriyas, or warriors; and Sudras, or workers. The Aryans monopolized the two upper castes, the Sudras being the Dravidian subject population. These castes were kept apart by a rigorous series of religious taboos. Intermarriage, partaking of food and drink, even physical propinquity, entailed ceremonial defilement sometimes inexpiable. Disobedience to these taboos was punished with the terrible penalty of "outcasting," whereby the offender did not merely fall to a lower rank in the caste hierarchy but sank even below the Sudra and became a "Pariah," or man of no-caste, condemned to the most menial and revolting occupations, and with no rights which even the Sudra was bound to respect.