Once you grant that there is a necessity of rebirth then many questions arise. In fact it is this question which is the central theme of Kathopnishad. The story is that Nachiketas is a son of a Brahmin who has done a sacrifice and in the sacrifice he has offered his wealth and his son Nachiketas is sitting near by. And he finds that the wealth of his father consisted only of cows which have lived their full life and had become worn out, all the milk that they had they have given and they are quite worthless now and it is these that the Brahmin is offering as sacrifice. The son becomes very perplexed and worried and he feels that if you want to make sacrifices you should make good sacrifice, the things which are useful and have real valuable. To prevent the father from making sacrifices of useless things he puts a question to his father and says father to whom do you want to sacrifice me because he is a young boy with a lot of life to live and if he is sacrificed there will be meaning in it. So, inducing his father to say alright, I sacrifice you, he will earn some merit. Father is annoyed with his question. Then the boy asked for a second time and he asked for a third time. The father becomes very angry and in anger he says I give you to Death, to Yama I give you. As he utters these words, the soul of Nachiketas is transported to the house of Yama. He arrives at Yama’s house where Yama is not present for three days. And the attendants of Yama at Yama’s arrival after three days, inform Yama that a young Brahmin has arrived at his house and if you do not treat him well, it is not good for you. Now, you request him to come in and propitiate him. Yama says, since you have remained for three nights in my house I will give you three boons. Choose them. Nachiketas then asks for three boons. The first boon is when I return from here my father is very pleased with me. The second, tell me what is the nature of celestial fire, celestial Agni? And this question Yama answers. The third question he asks is we are told that there is a debate that when man passes out then he no more is or he is. Now that you know, you are the only one who knows the real truth please tell me what happens really.
This question is such an important question that Yama does not want to answer it. Such a secret question and such a secret knowledge to which an answer is to be given that he does not feel this boy should be given the knowledge and he says even Gods do not know. So why do you want an answer to this question. You select any other boon and I will give you. The boy says, what even Gods do not want to know, I want to know and I want to have that fulfillment.
Yama says I will give anything – wealth, beautiful wives, children, and so much of property that generations after generations there will be no lack of it. Ask for any such boon. He says then what is the end of all pleasures, nothing? But this knowledge which is so precious I want. Then Yama says you have pleased my heart. There are two ways, shreyas and preyas. I offered you preyas and all that is pleasant and you did not accept it but you held on to shreyas – to that which is really worthwhile. I am pleased with you and will therefore let you have this knowledge, then follows a dialogue which is a very difficult dialogue. This is the question Sri Aurobindo says, if rebirth is necessary, is the necessity of the universal significance then many questions arise.
“There arises the first question of the process of rebirth; if that process is not quickly successive, birth immediately following death of the body so as to maintain an uninterrupted series of lives of the same person, if there are intervals, that in its turn raises the question of the principle and process of the passage to other worlds, which must be the scene of these intervals, and the return to earth–life. A third question is the process of the spiritual evolution itself and the mutations which the soul undergoes in its passage from birth to birth through the stages of its adventure.”
The first question is what is the process of rebirth? Who is reborn, how is one reborn? In what form is he reborn?
The second is, is rebirth immediately successive. There are two notions which are running in the world amongst those who believe in rebirth, not sufficiently reconciled. According to one view you leave this body and you are immediately reborn into another body. According to the other view once you come out of the body you go through experiences of pleasure and pain according to whether you have been good or bad on this earth. If you have been good you go to heaven and pleasures of some kind, otherwise you will be chastised and sent to hell for some time. And when this is over you take another birth. This is a popular notion, not necessarily scientifically verifiable. These are the current notions. We have to arrive at a very scientific conclusion on this subject. Is rebirth immediately successive or if not immediately successive then what happens to the soul in the interval?
The third question is that in the whole process of dying, coming out of the body, passing to wherever one has to pass after the death of the body, returning to the new body; what is it that the soul gains and how does it evolve itself. What is the process of its evolution? What role does nature play and what role does the soul play in the evolution of consciousness, which is the real purpose. These are the three questions that arise.