The Arithmetics of Reincarnation / Rebirth

Yesterday Ajahn Brahm gave a talk on the topic of Reincarnation. In his talk he referred the question people usually make on how could rebirth/reincarnation be possible as the world’s population is now as big as it has ever been.

I remember that back some few years ago Ajahn Brahmali (@brahmali) and Ajahn Sujato (@sujato) got asked or talked about that question (my memory is not that good) in one of the workshops on Karma and Rebirth held in Dhammaloka.

And I remember that we all checked the numbers and came up across a well done study to debunk the factoid that arose back in the 70s “that 75 percent of the people who had ever been born were alive at that moment”.

Here is the video featuring the expert who double-checked the maths and arithmetics of this interesting question:

In a nutshell, the most recent calculations point to very interesting conclusion: since the begining of humankind (as a separate specie) something around ~108 billion people have ever lived on Earth!

At ~7.5 billion people today, the current world population corresponds to a mere ~7% of the whole figure!

Most interestingly, as per the table shown in the link above, some ~47 billion of the total 108 billion were born and died between 8000 B.C. and 1 A.D.!!! This corresponds to 43% of the total figure!

Bottom line is:

  • there is absolutely nothing wrong with the arithmetic/maths of reincarnation/rebirth!
  • And most of the dead humans “in stock” were born in ancient times!

PS: @brahmali could you please kindly help me delivering this study and its figures to Ajahn Brahm in person? I think he would like to refer to that as well whenever talking about this topic again! :slight_smile:


Not to mention the possibility of different worlds in other galaxies (or our own). Scientists estimate that there are 100 billion galaxies that we know of. According to your numbers, that’s about 1 galaxy for every human that’s ever lived.

And even that’s not to mention the possibility of multiple universes, which is not sci-fi but a legitimate theory in physics.






Thank you for this beautiful clarification of the mathematical possibilities in relation to rebirth! I think this may definitely help away those who are on the fence about their belief in rebirth.

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And rebirth is not limited to the human realm. There are quadrillions of other animals just on Earth (or some other large number this size or greater). The old adage that “there are not enough ‘souls’ to go around” is not mathematically true.


Sounds exciting! Postpone Nibbana until I see all of the other galaxies, using the MN 120 method. :airplane:

Actually this estimate was recently upgraded to 2 trillion galaxies in the observable universe.


The arithmetics don’t take into account the fact that there was a time when there were no humans at all, and it wasn’t all that long ago compared to the age of Earth. Were the cyanobacteria of 3.5 billion years ago also reincarnated? If so, from what?

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Not sure one can definitely answer that unless he wins the lottery and as a bonus to awakening the three superhuman knowledges are attained.

Despite that, nevertheless, it is interesting taking in consideration what the Agañña Sutta (DN27) suggests in a context of a suggested cyclical universe:

There comes a time, Vāseṭṭha, when, sooner or later, after the lapse of a long, long period, this world passes away. And when this happens, beings have mostly been reborn in the World of Radiance; and there they dwell, made of mind, feeding on rapture, self-luminous, traversing the air, continuing in glory; and thus they remain for a long, long period of time.

There comes also a time, Vāseṭṭha, when sooner or later this world begins to re-evolve. When this happens, beings who had deceased from the World of Radiance, usually come to life as humans. And they become made of mind, feeding on rapture, self-luminous, traversing the air, continuing in glory, and remain thus for a long, long period of time.

Okay, but:
“How does one attend inappropriately: ‘Was I in the past? Was I not in the past? What was I in the past? How was I in the past? Having been what, what was I in the past? Shall I be in the future? Shall I not be in the future? What shall I be in the future? How shall I be in the future? Having been what, what shall I be in the future?’ Or else one is inwardly perplexed about the immediate present: ‘Am I? Am I not? What am I? How am I? Where has this being come from? Where is it bound?’”
Majjhima Nikaya, #2


But you are the one asking! :grin:

Not 100% related but nonetheless interesting (at least to me), I would like to take the chance to share this video with you all! :slight_smile:

By not attending to, not knowing, not directly seeing paticcasamuppada. By not having entered the stream, by being caught up in a thicket of views, by not opening the dustless stainless Dhamma eye.

Then to Sariputta the wanderer, as he heard this exposition of Dhamma, there arose the dustless, stainless Dhamma eye: Whatever is subject to origination is all subject to cessation.
Mv I.23.5

Then this happens:

“When, bhikkhus, a noble disciple has clearly seen with correct wisdom as it really is this dependent origination and these dependently arisen phenomena, it is impossible that he will run back into the past, thinking: ‘Did I exist in the past? Did I not exist in the past? What was I in the past? How was I in the past? Having been what, what did I become in the past?’ Or that he will run forward into the future, thinking: ‘Will I exist in the future? Will I not exist in the future? What will I be in the future? How will I be in the future? Having been what, what will I become in the future?’ Or that he will now be inwardly confused about the present thus: ‘Do I exist? Do I not exist? What am I? How am I? This being—where has it come from, and where will it go?’ sn12.20

:wink: :anjal:

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