It would, indeed, be admissible, if one had any certainty in regard to the age of the different parts of the Rig Veda, simply to divide the hymns into early, middle, and late, as they are sometimes divided in philological works, but here one rests on the weakest of all supports for historical judgment, a linguistic and metrical basis, when one is ignorant alike of what may have been accomplished by imitation, and of the work of those later priests who remade the poems of their ancestors.

Best then, because least hazardous, appears to be the method which we have followed, namely, to take up group by group the most important deities arranged in the order of their relative importance, and by studying each to arrive at a fair understanding of the pantheon as a whole.  The Hindus themselves divided their gods into highest, middle, and lowest, or those of the upper sky, the atmosphere, and the earth.  This division, from the point of view of one who would enter into the spirit of the seers and at the same time keep in mind the changes to which that spirit gradually was subjected, is an excellent one.  For, as will be seen, although the earlier order of regard may have been from below upwards, this order does not apply to the literary monuments.  These show on the contrary a worship which steadily tends from above earthwards; and the three periods into which may be divided all Vedic theology are first that of the special worship of sky-gods, when less attention is paid to others; then that of the atmospheric and meteorological divinities; and finally that of terrestrial powers, each later group absorbing, so to speak, the earlier, and therewith preparing the developing Hindu intelligence for the reception of the universal god with whom closes the series.

Other factors than those of an inward development undoubtedly were at work in the formation of this growth.  Especially prominent is the amalgamation of the gods of the lower classes with those of the priest-hood.  Climatic environment, too, conditioned theological evolution, if not spiritual advance.  The cult of the mid-sphere god, Indra, was partly the result of the changing atmospheric surroundings of the Hindus as they advanced into India.  The storms and the sun were not those of old.  The tempests were more terrific, the display of divine power was more concentrated in the rage of the elements; while appreciation of the goodness of the sun became tinged with apprehension of evil, and he became a deadly power as well as one beneficent.  Then the relief of rain after drought gave to Indra the character of a benign god as well as of a fearful one.  Nor were lacking in the social condition certain alterations which worked together with climatic changes.  The segregated mass of the original people, the braves that hung about the king, a warrior-class rapidly becoming a caste, and politically the most important caste, took the god of thunder and lightning for their god of battle.  The fighting race naturally exalted