Only he who has a co-ordinated understanding of both the visible and the invisible, of matter and spirit, of activity and that which is behind activity, conquers Nature and thus overcomes death.
The idea of reward and punishment also springs from this law. Whatever we sow, we must reap. It cannot be otherwise. [...] If a person spends all his life in evil-thinking and wrongdoing, then it is useless for him to look for happiness hereafter; because our hereafter is not a matter of chance, but follows as the reaction of our present action. [...] We should, however, never lose sight of the fact that all these ideas of reward and punishment exist in the realm of relativity or finiteness. No soul can ever be doomed eternally through his finite evil deeds; for the cause and effect must always be equal. Thus we can see through our common sense that the theory of eternal perdition and eternal heaven is impossible and illogical, since no finite action can create an infinite result. Hence according to Vedanta, the goal of mankind is neither temporal pleasure nor pain, but Mukti or absolute freedom; and each soul is consciously or unconsciously marching towards this goal through the various experiences of life and death.
The Hereafter does not shine before those who are lacking in the power of discrimination and are easily carried away therefore by the charm of fleeting objects. As children are tempted by toys, so they are tempted by pleasure, power, name and fame. To them these seem the only realities. Being thus attached to perishable things, they come many times under the dominion of death. There is one part of us which must die; there is another part which never dies. When a man can identify himself with his undying nature, which is one with God, then he overcomes death.
Children (the ignorant) pursue external pleasures; (thus) they fall into the wide-spread snare of death. But the wise, knowing the nature of immortality, do not seek the permanent among fleeting things.
As long as man is overpowered by the darkness of ignorance, he is the slave of Nature and must accept whatever comes as the fruit of his thoughts and deeds. When he strays into the path of unreality, the Sages declare that he destroys himself; because he who clings to the perishable body and regards it as his true Self must experience death many times.