The basis of these views the Aryas brought with them into the valley of the Indus. Their name for the deity of light--_deva_, from _div_, to shine--is found among the Greek, Italian, Lettish, and Celtic nations in the forms [Greek: theoi], _dii_, _diewas_, and _dia_; it recurs in the Zeus (_dyaus_) of the Greeks, and the Jupiter (_dyauspitar_) of the Romans. The god of the upper air is with the Aryas Varuna, the Uranos of the Greeks. And these were not the only ideas possessed by the Aryas before their immigration. When they had broken off from the original stem of the Indo-European tribes, they must for a time have lived in union with another branch of the same stem, which inhabited the table-land of Iran, and only after a long period of union did they become a nation, and emigrate to the East. The nucleus of the view of the nature and action of the gods is identical in the Aryas and the tribes of Iran to such a degree that it can only have grown up in a common life. In both it lies in the struggle and opposition in which the spirits of light stand to the spirits of darkness, the spirits who give water to the spirits who parch up all things--in the contest of good and evil gods. It is assistance and protection against the evil spirits, the boon of light and water, which is sought for in the worship of both nations. The names of the deities of light, which the Indians and the Iranians serve, are the same. Mitra, Aryaman, Bhaga, Ushas are invoked on the Indus and Sarasvati as well as on the Hilmend, in Bactria and Media. Here, as there, the beneficent morning wind which drives away the clouds of night is called Vayu; the same drink offerings were offered under the same names in both nations to the good gods. With the Indians Atharvan lights the sacrificial fire;[67] among the Iranians the fire priests are called Athravas. The chief of the evil spirits, against which the good spirits have to contend, is called Veretra among the Iranians, and Vritra among the Indians; another evil spirit is called Azhi (_Aji_) in one nation, Ahi in the other. Such was the development given to the common inheritance from the parent stock, attained while the Airyas and Aryas lived together; and after the community was broken up, and the two nations became separated, those views received a peculiar shape in each. The point in this special development reached by the Aryas while yet in the Panjab we know from the poems of the Rigveda.