It is curious corroboration of this alleged British origin of Druidism that the ancient Irish also believed their Druidism to have come from the sister island. Their heroes and seers are described as only gaining the highest knowledge by travelling to Alba.[37] However this may be, we may take it as certain that this Druidism was the accepted religion of the Celtic race. Certain scholars look deeper for its origin, holding its dark superstitions and savage rites to bear the stamp of lower minds than those of the poetic and manly Celts. Professor Rhys inclines to see three forms of religion in the British Islands at the time of the Roman invasion: the “Druidism” of the Iberian aborigines; the pure polytheism of the Brythons, who, having come later into the country, had mixed but little with the natives; and the mingled Aryan and non-Aryan cults of the Goidels, who were already largely amalgamated with them.[38] But many authorities dissent from this view, and, indeed, we are not obliged to postulate borrowing from tribes in a lower state of culture, to explain primitive and savage features underlying a higher religion. The “Aryan” nations must have passed, equally with all others, through a state of pure savagery; and we know that the religion of the Greeks, in many respects so lofty, sheltered features and legends as barbarous as any that can be attributed to the Celts.[39] Of the famous teaching of the Druids we know little, owing to their habit of never allowing their doctrines to be put into writing. Caesar, however, roughly records its scope. “As one of their leading dogmas”, he says, “they inculcate this: that souls are not annihilated, but pass after death from one body to another, and they hold that by this teaching men are much encouraged to valour, through disregarding the fear of death. They also discuss and impart to the young many things concerning the heavenly bodies and their movements, the size of the world and of our earth, natural science, and of the influence and power of the immortal gods.”[40] The Romans seem to have held their wisdom in some awe, though it is not unlikely that the Druids themselves borrowed whatever knowledge they may have had of science and philosophy from the classical culture. That their creed of transmigration was not, however, merely taken over from the Greeks seems certain from its appearance in the ancient Gaelic myths. Not only the “shape-shifting” common to the magic stories of all nations, but actual reincarnation was in the power of privileged beings. The hero Cuchulainn was urged by the men of Ulster to marry, because they knew “that his rebirth would be of himself”,[41] and they did not wish so great a warrior to be lost to their tribe. Another legend tells how the famous Finn mac Coul was reborn, after two hundred years, as an Ulster king called Mongan.[42]