The individual soul takes again a mortal vehicle. The individual soul takes again a mortal vehicle. The word 'transmigration' means passing from one plane to another-passing into a new body. The doctrine of rebirth is a corollary to the law of Karma. The differences of disposition that are found between one individual and another must be due to one's respective past actions.
Past action implies past birth.
Further, all your Karmas cannot certainly bear fruit in this birth alone. Therefore, there must be another birth for enjoying the remaining actions. Each soul has a series of births and deaths. Births and deaths will continue till you attain knowledge of the Self. You do not come into the world in total forgetfulness and in utter darkness.