a regular name of the moon, which is regarded as being consumed by the gods, and consequently waning till it is filled up again by the sun. This somewhat remarkable coalescence of Soma with the moon doubtless sprang from the hyperbolical terms in which the poets of the Rigveda dwell on Soma's celestial nature and brilliance, which they describe as dispelling darkness. They sometimes speak of it as swelling in the waters, and often refer to the sap as a "drop" (indu). Comparisons with the moon would thus easily suggest themselves. In one passage of the Rigveda, for instance, Soma in the bowls is said to appear like the moon in the waters. The mystical speculations with which the Soma poetry teems would soon complete the symbolism.
A comparison of the Avesta with the Rigveda shows clearly that soma was already an important feature in the mythology and cult of the Indo-Iranian age. In both it is described as growing on the mountains, whence it is brought by birds; in both it is king of plants; in both a medicine bestowing long life and removing death. In both the sap was pressed and mixed with milk; in both its mythical home is heaven, whence it comes down to earth; in both the draught has become a mighty god; in both the celestial Soma is distinguished from the terrestrial, the god from the beverage. The similarity goes so far that Soma and Haoma have even some individual epithets in common.
The evolution of thought in the Rigvedic period shows a tendency to advance from the concrete to the abstract. One result of this tendency is the creation of abstract deities, which, however, are still rare, occurring for the most part in the last book only. A few of them are deifications of abstract nouns, such as Çraddhā
