The doctrine of Metempsychosis was believed in by the Greeks and the Celts. According to Herodotus the former borrowed it from Egypt, and although some have cast doubt on the existence of the theory in Egypt, there are evidences that it obtained there as in early Aryanized India among sections of the people.[161] It is possible that the doctrine is traceable to a remote racial influence regarding which no direct evidence survives. [161] See _Egyptian Myth and Legend_. All that we know definitely regarding the definite acceptance of the theory in India is that in _Satapatha Brahmana_ it is pointedly referred to as a necessary element of orthodox religion. The teacher declares that those who perform sacrificial rites are born again and attain to immortality, while those who neglect to sacrifice pass through successive existences until Death ultimately claims them. According to Upanishadic belief the successive rebirths in the world are forms of punishment for sins committed, or a course of preparation for the highest state of existence. In the code of Manu it is laid down, for instance, that he who steals gold becomes a rat, he who steals uncooked food a hedgehog, he who steals honey a stinging insect; a murderer may become a tiger, or have to pass through successive states of existence as a camel, a dog, a pig, a goat, &c.; other wrongdoers may have to exist as grass, trees, worms, snails, &c. As soon as a man died, it was believed that he was reborn as a child, or a reptile, as the case might be. Sufferings endured by the living were believed to be retribution for sins committed in a former life. Another form of this belief had evidently some connection with lunar worship, or, at any rate, with the recognition of the influence exercised by the moon over life in all its phases; it is declared in the _Upanishads_ that “all who leave this world go directly to the moon. By their lives its waxing crescent is increased, and by means of its waning it brings them to a second birth. But the moon is also the gate of the heavenly world, and he who can answer the questions of the moon is allowed to pass beyond it. He who can give no answer is turned to rain by the moon and rained down upon the earth. He is born again here below, as worm or fly, or fish or bird, or lion, or boar or animal with teeth, or tiger, or man, or anything else in one or another place, according to his works and his knowledge.”[162] [162] Paul Deussen's translation.