Sri Aurobindo sums up the preceding discussion of this chapter with the concluding paragraph. He systematically revisits each of the options that were reviewed, and shows that for many of them, rebirth is not a necessary conclusion, but that these options themselves do not adequately explain the reality of life and consciousness as we experience them.
Regarding rebirth, then, “it is an inevitable logical conclusion if there exists at the same time an evolutionary principle in the Earth-Nature and a reality of the individual soul born into evolutionary Nature.”
and further, “But if there is an evolution of consciousness in an evolutionary body and a soul inhabiting the body, a real and conscious individual, then it is evident that it is the progressive experience of that soul in Nature which takes the form of this evolution of consciousness: rebirth is self-evidently a necessary part, the sole possible machinery of such an evolution. It is as necessary as birth itself; for without it birth would be an initial step without a sequel, the starting of a journey without its farther steps and arrival. It is rebirth that gives to the birth of an incomplete being in a body its promise of completeness and its spiritual significance.”
Sri Aurobindo, The Life Divine, Book 2, Part 2, Chapter 20, The Philosophy of Rebirth