The debt of Śaṅkara to Buddhism is an interesting question. He indited polemics against it and contributed materially to its downfall, but yet if the success of creeds is to be measured by the permanence of ideas, there is some reason for thinking that the vanquished led the conqueror captive. Śaṅkara's approval both in theory and in practice of the monastic life is Buddhistic rather than Brahmanical.[520] The doctrines of Mâyâ and the distinction between higher and lower truth, which are of cardinal importance in his philosophy, receive only dubious support from the Upanishads and from Bâdarâyaṇa, but are practically identical with the teachings of the Mâdhyamika School of Buddhism and it was towards this line of thought rather than towards the theism of the Pâśupatas or Bhâgavatas that he was drawn. The affinity was recognized in India, for Śaṅkara and his school were stigmatized by their opponents as Buddhists in disguise.[521] 2 The reader will perhaps have noticed that up to the career of Śaṅkara we have been concerned exclusively with northern India, and even Śaṅkara, though a native of the south, lived much in the north and it was the traditional sacred lore of the north which he desired to establish as orthodoxy. Not only the older literature, Brahmanic as well as Buddhist, but most of the Purâṇas ignore the great stretch of Dravidian country which forms the southern portion of the peninsula and if the Râmâyaṇa sings of Râma's bridge and the conquest of Laṅka this is clearly an excursion into the realms of fancy. Yet the Dravidian districts are ample in extent, their monuments are remarkable, their languages are cultivated, and Tamil literature possesses considerable interest, antiquity and originality. Unfortunately in dealing with these countries we experience in an unusually acute form the difficulties which beset every attempt to trace the history of ideas in India, namely, the absence of chronology. Before 1000 A.D. materials for a connected history are hardly accessible. There are, however, many inscriptions and a mass of literature (itself of disputable date) containing historical allusions, and from these may be put together not so much a skeleton or framework as pictures of ancient life and thought which may be arranged in a plausible order.