Though it has touched excellence in most of its branches, Sanskrit literature has mainly achieved greatness in religion and philosophy. The Indians are the only division of the Indo-European family which has created a great national religion--Brahmanism--and a great world-religion--Buddhism; while all the rest, far from displaying originality in this sphere, have long since adopted a foreign faith. The intellectual life of the Indians has, in fact, all along been more dominated by religious thought than that of any other race. The Indians, moreover, developed independently several systems of philosophy which bear evidence of high speculative powers. The great interest, however, which these two subjects must have for us lies, not so much in the results they attained, as in the fact that every step in the evolution of religion and philosophy can be traced in Sanskrit literature. The importance of ancient Indian literature as a whole largely consists in its originality. Naturally isolated by its gigantic mountain barrier in the north, the Indian peninsula has ever since the Aryan invasion formed a world apart, over which a unique form of Aryan civilisation rapidly spread, and has ever since prevailed. When the Greeks, towards the end of the fourth century B.C., invaded the North-West, the Indians had already fully worked out a national culture of their own, unaffected by foreign influences. And, in spite of successive waves of invasion and conquest by Persians, Greeks, Scythians, Muhammadans, the national development of the life and literature of the Indo-Aryan race remained practically unchecked and unmodified from without down to the era of British occupation. No other branch of the Indo-European stock has experienced an isolated evolution like this. No other country except China can trace back its language and literature, its religious beliefs and rites, its domestic and social customs, through an uninterrupted development of more than three thousand years.