There have been philosophers through history who have recognised the necessity of rebirth as a mechanism for the development of the soul. Some of those believed that the soul could jump back and forth between human and animal births and they devised elaborate frameworks of how actions in a human incarnation could push the soul back into an animal birth in a future lifetime. There was a rough correspondence to be seen between moral and ethical ideals and the “punishment” endured by a soul who transgressed any of these rules, by a subsequent animal birth to live out basically the effect that the soul had created with its immoral or unethical actions in a particular lifetime.
Sri Aurobindo takes up this question, first by validating the evolution of the soul across successive births, but then examining more closely the issues involved in the leap from animal to human incarnations to determine the validity of the idea that the soul can go backwards into animal forms once human birth has been attained.
“…human birth is a term at which the soul must arrive in a long succession of rebirths and that it has had for its previous and preparatory terms in the succession the lower forms of life upon earth; it has passed through the whole chain that life has strung in the physical universe on the basis of the body, the physical principle. Then the farther question arises whether, humanity once attained, this succession of rebirths still continues and, if so, how, by what series or by what alternations. And, first, we have to ask whether the soul, having once arrived at humanity, can go back to the animal life and body, a retrogression which the old popular theories of transmigration have supposed to be an ordinary movement. It seems impossible that it should so go back with any entirety, and for this reason that the transit from animal to human life means a decisive conversion of consciousness, quite as decisive as the conversion of the vital consciousness of the plant into the mental consciousness of the animal. It is surely impossible that a conversion so decisive made by Nature should be reversed by the soul and the decision of the spirit within her come, as it were, to naught.”
Sri Aurobindo, looking at the occult thread that ties together the entirely evolutionary process, determines that the development of consciousness, and the complexity of organisation that goes with it, makes it unlikely in the extreme that such a reversion could take place.
We shall continue to explore this theme and its other aspects in the next post.
Sri Aurobindo, The Life Divine, Book 2, Part 2, Chapter 20, The Philosophy of Rebirth