The Asuras advanced as the Kâlpic age advanced. There was no end of advancement from the standpoint of self. There is no big jump from individual self to universal self. Though the essential idea of spirituality is unity and the essential idea of materiality is diversity, the one idea develops into the other idea, by an ever widening view of things. Our duties enlarge. Our relations increase. The range of life widens, till it includes the life in Svarga. Vedic Yajna is then performed, though from a pure motive of self-advancement. The advanced self comes very near to the universal self. The performance of Vedic sacrifices is Asuric in so far as it is selfish, but it minimises the self of earthly existence, and gives a transitory character to our worldly joys and sufferings, and it gives the idea of an enlarged self, of widened existence and of higher duties. The Karma Kânda of the Vedas therefore opens the door widely to real spiritual life. This explains why Vishvarupa, an Asura, guided the Devas for some time. The three heads of Vishvarupa represent the three Vedas. The swallow head is the Rik, the sparrow head is the Sâman, and the Tittiri head is proverbially the Yajur. This refers to the prevalence of Karma Kânda. But when better times came, Indra killed Vishva-rûpa. The place of Vishva-rûpa was however speedily taken, up by Vritra. And Indra had recourse to Atharva, the fourth Veda and to Dadhîchi, a votary (represented as the son) of Atharva Veda, the very ideal of self-sacrifice. And who is this Vritra? The Vedas say: — _"Sa imân lokân Avrinot etat Vritrasya Vritratvam."_ He spread over (_vri_) all these Lokas, this is the Vritraship of Vritra. The Bhâgavata says: — "These Lokas are spread over by him in the form of Tvashtri’s Tapas. Hence he is called Vritra." VI. — 9-xviii. The invocation of Tvashtri is thus described in the Bhâgavata: — "Rise up, O Indra — Shatru, never give up enmity." VI — 9-xii. The word _shatru_ means enemy. Tvastri meant to say "he who is to become the enemy of Indra." But by proper grammatical construction, the expression means, he of whom Indra is to become the enemy. The invocation was therefore defective and it produced a contrary result. Pânini points this out as an apt illustration of what bad grammar leads to. The Vedas thus speak of the invocation: — "As he said-_Svâha_! O Indra-Shatru! rise up — so Indra became the enemy of Vritra." Notwithstanding his wisdom, Chitra-ketu was anxious to have a son. He wept bitterly, when the son was lost. He was a votary of Sankarshana, who presides over Ahankâra or Egoism. So by devotion he became the king of the Vidyâdharas. This selfish devotion, the worship of Gods for the gratification of selfish aspiration, which is so universal, is Vritra.