In later times, the strict adherence to caste duties would naturally receive considerable support from the belief in the transmigration of souls, already prevalent before Buddha's time, and from the very general acceptance of the doctrine of karma (" deed "), or retribution, according to which a man's present station and manner of life are the result of the sum-total of his actions and thoughts in his former existence; as his actions here will again, by the same automatic process of retribution, determine his status and condition in his next existence.
In India, the (still unexplained) rise of the doctrine of transmigration hindered belief.
Curiously, Buddhism itself is ruled by the ghost or shadowy remainder of belief in transmigration - Karma.
This belief - the transmigration of the soul, after the death of the body, into other bodies, either of men, beasts or gods - is part of the animistic creed so widely found throughout the world that it was probably universal.
Once at a village where he rested the Blessed One (Buddha) addressed his brethren and said: "It is through not understanding and grasping four Noble Truths, 0 brethren, that we have had to run so long, to wander so long in this weary path of transmigration, both you and I."