Among all the classical theories of life after death, the one that seems to be most consistent with naturalism is the ancient Buddhist concept of rebirth. This concept is developed in Theraveda Buddhism. Theravedic Buddhism is an atheistic (or non-theistic) religion. Rebirth is linked to the Theravedic doctrines of impermanence and no-self. These doctrines imply that there are no permanent substances that endure either through one life or across different lives. There are no immaterial thinking substances (no Cartesian minds) that pass from life to life or body to body. Rebirth is not the transmigration of immaterial thinking substances:
As there is no permanent, unchanging substance, nothing passes from one moment to the next. So quite obviously, nothing permanent or changing can pass or transmigrate from one life to the next. It is a series that continues unbroken, but changes every moment. The series is, really speaking, nothing but movement. It is like a flame that burns through the night: it is not the same flame nor is it another. A child grows up to be a man of sixty. Certainly the man of sixty is not the same as the child of sixty years ago, nor is he another person. Similarly, a person who dies here and is reborn elsewhere is neither the same person nor another. It is the continuity of the same series. (Rahula, 1974: 34)
As an illustration of rebirth (which is not reincarnation), consider the eternal return of the same. The eternal return (also known as eternal recurrence) is the theory that physical reality has a cyclical pattern. The same pattern of events repeats itself over and over. The repetition is exact – there is no variation from cycle to cycle. Eternal recurrence is an old idea. The ancient Greek philosopher Eudemus tells his students: “If one were to believe the Pythagoreans, with the result that the same individual things will recur, then I shall be talking to you again sitting as you are now, with this pointer in my hand, and everything else will be just as it is now” (Kirk & Raven, 1957: frag. 272).
More recently, eternal recurrence was popularized by Nietzsche. And Nietzsche, as is well-known, is an atheistic philosopher. Nietzsche uses his character Zarathustra to talk about eternal recurrence. Zarathustra has two animals, an eagle and a snake. They tell him that they understand his theory of eternal recurrence:
Behold, we know what you teach: that all things recur eternally and we ourselves with them, and that we have already existed an infinite number of times before and all things with us. You teach that there is a great year of becoming, a colossus of a year: this year must, like an hour-glass, turn itself over again and again, so that it may run down and run out anew. So that all these years resemble one another, in the greatest things and in the smallest, so that we ourselves resemble ourselves in each great year, in the greatest things and in the smallest. And if you should die now, O Zarathustra: behold, we know too what you would then say to yourself . . . “Now I die and decay” you would say, “and in an instant I shall be nothingness. Souls are as mortal as bodies. But the complex of causes in which I am entangled will recur — it will create me again! I myself am part of these causes of the eternal recurrence. I shall return, with this sun, with this earth, with this eagle, with this serpent — not to a new life or a better life or a similar life: I shall return eternally to this identical and self-same life, in the greatest things and in the smallest, to teach once more the eternal recurrence of all things.” (Nietzsche, 1974: III: 13/2)
If the eternal return of the same is true (which is not to say that it is true), then your life is just one member of a two-way infinite series of exactly similar lives. On every natural cycle, you are born, you live, you die; and on every next cycle, you will be born again, you will live exactly the same life again, and you will die again. There is no immaterial thinking substance (no Cartesian mind) that moves from life to life. Of course, all these distinct lives share exactly the same pattern. Each of these lives is a series of stages like a movie is a series of photograhs or like a book is a series of pages. And each stage is a body that exists at exactly one instant of time. All of these bodies share the same form. If the soul is the form of the body, then they all share the same soul. All your past and future recurrence twins all share the same genotype. The soul is just a pattern that all your past and future bodies share. But there is no immaterial thinking substance that moves from body to body. All your lives are entirely material processes.
Previously: The Soul is the Form of the Body
Kirk, G. S. & Raven, J. E. (1957) The Presocratic Philosophers: A Critical History with a Selection of Texts. New York: Cambridge University Press.
Nietzsche, F. (1974) Thus Spoke Zarathustra. Trans. R. J. Hollingdale. New York: Penguin Books.
Rahula, W. (1974) What the Buddha Taught: Revised and Expanded Edition with Texts from Suttas and Dhammapada. New York: Grove / Atlantic.