Fire, caloric, or heat in some form was, among the ancient nations, supposed to be the animus mundi.  In Egypt, as we have seen, Osiris, the principal deity, was a form of Ra, the sun-god.  In Assyria, Asshur, the substitute for Ra, was the supreme deity.  In India we find Mitra, and in Persia Mithra, the sun-god, among the prominent deities, as Helios was among the Greeks, and Phoebus Apollo among the Romans.  The sun was not always the supreme divinity, but invariably held one of the highest places in the Pagan pantheon.

It is probable that the religion of the common progenitors of the Hindus, Persians, Greeks, Romans, Kelts, Teutons, and Slavs, in their hard and sterile home in Central Asia, was a worship of the powers of Nature verging toward pantheism, although the earliest of the Vedas representing the ancient faith seem to recognize a supreme power and intelligence—­God—­as the common father of the race, to whom prayers and sacrifices were devoutly offered.  Freeman Clarke quotes from Mueller’s “Ancient Sanskrit Literature” one of the hymns in which the unity of God is most distinctly recognized:—­

“In the beginning there arose the Source of golden light.  He was the only Lord of all that is.  He established the earth and sky.  Who is the God to whom we shall offer our sacrifices?  It is he who giveth life, who giveth strength, who governeth all men; through whom heaven was established, and the earth created.”

But if the Supreme God whom we adore was recognized by this ancient people, he was soon lost sight of in the multiplied manifestations of his power, so that Rawlinson thinks[2] that when the Aryan race separated in their various migrations, which resulted in what we call the Indo-European group of races, there was no conception of a single supreme power, from whom man and nature have alike their origin, but Nature-worship, ending in an extensive polytheism,—­as among the Assyrians and Egyptians.

[Footnote 2:  Religions of the Ancient World, p. 105.]

As to these Aryan migrations, we do not know when a large body crossed the Himalaya Mountains, and settled on the banks of the Indus, but probably it was at least two thousand years before Christ.  Northern India had great attractions to those hardy nomadic people, who found it so difficult to get a living during the long winters of their primeval home.  India was a country of fruits and flowers, with an inexhaustible soil, favorable to all kinds of production, where but little manual labor was required,—­a country abounding in every kind of animals, and every kind of birds; a land of precious stones and minerals, of hills and valleys, of majestic rivers and mountains, with a beautiful climate and a sunny sky.  These Aryan conquerors drove before them the aboriginal inhabitants, who were chiefly Mongolians, or reduced them to a degrading vassalage.  The conquering race was white, the conquered was dark, though not black; and this difference of color was one of the original causes of Indian caste.