The Vedic literature is divided by Müller into four periods, namely, those of the Chhandas, Mantra, Brâhmana, and Sûtras. The Chhandas period contains the oldest hymns of the oldest, or Rig-Veda. To that of the Mantras belong the later hymns of the same Veda. But the most modern of these are older than the Brâhmanas. The Brâhmanas contain theology; the older Mantras are liturgic. Müller says that the Brâhmanas, though so very ancient, are full of pedantry, shallow and insipid grandiloquence and priestly conceit. Next to these, in the order of time, are the Upanishads. These are philosophical, and almost the only part of the Vedas which are read at the present time. They are believed to contain the highest authority for the different philosophical systems, of which we shall speak hereafter. Their authors are unknown. More modern than these are the Sûtras. The word "Sûtra" means _string_, and they consist of a string of short sentences. Conciseness is the aim in this style, and every doctrine is reduced to a skeleton. The numerous Sûtras now extant contain the distilled essence of all the knowledge which the Brâhmans have collected during centuries of meditation. They belong to the non-revealed literature, as distinguished from the revealed literature,--a distinction made by the Brâhmans before the time of Buddha. At the time of the Buddhist controversy the Sûtras were admitted to be of human origin and were consequently recent works. The distinction between the Sûtras and Brâhmanas is very marked, the second being revealed. The Brâhmanas were composed by and for Brahmans and are in three collections. The Vedângas are intermediate between the Vedic and non-Vedic literature. Pânini, the grammarian of India, was said to be contemporary with King Nanda, who was the successor of Chandragupta, the contemporary of Alexander, and therefore in the second half of the fourth century before Christ. Dates are so precarious in Indian literature, says Max Müller, that a confirmation within a century or two is not to be despised. Now the grammarian Kâtyâyana completed and corrected the grammar of Pânini, and Patanjeli wrote an immense commentary on the two which became so famous as to be imported by royal authority into Cashmere, in the first half of the first century of our era. Müller considers the limits of the Sûtra period to extend from 600 B.C. to 200 B.C. Buddhism before Asoka was but modified Brahmanism. The basis of Indian chronology is the date of Chandragupta. All dates before his time are merely hypothetical. Several classical writers speak of him as founding an empire on the Ganges soon after the invasion of Alexander. He was grandfather of Asoka. Indian traditions refer to this king. Returning to the Brâhmana period, we notice that between the Sûtras and Bârahmanas come the Aranyakas, which are books written for the recluse. Of these the Upanishads, before mentioned, form part. They presuppose the existence of the Brâhmanas.