Let's take that person's subjective experience of the universe is given. If we take for example one particular person - lets say the person that is reasoning about this question (denoted with I in the rest of the text), we could say that: "because I'm having various kind of experiences about the universe, I would say for myself that I'm conscious."

I'm interested in this question:

How often, during the vast history of universe, do I get the chance to be conscious?

What confuses me about this question is the fact that all possible answers are in some ways unsatisfactory. Let's consider two extremes and few consequences that stem from them:

  1. It happened just once and I got one chance for these experiences to be lived through...

    • Consequence: We could say that something impossible or at least very very improbable happened in the universe, that permitted me to be conscious and universe usually doesn't allow for these impossibilities to happen. I would argue that something like this happening would be equal to miracles from religious stories, that should not be happening in the universe.
  2. It's happening all the time...

    • Consequence: Not only does subjective consciousness that I'm experiencing gets "reincarnated", but is also subject to experiencing the universe in parallel (becoming conscious as someone else for example, while still being conscious "in one body").

I'm interested if someone has already thought about something similar, and the results this line of reasoning produces. But I would assume that my argument is flawed in some way and would like to hear where I'm mistaken.

  • well if you can attach a number to X 1/X chance of you being conscious Just be glad the universe is infinite.
    – user3066
    Jan 28, 2013 at 19:20

2 Answers 2


You're just making a simple but intuitively appealing error in conflating a posteriori and a priori probabilities.

I have a handful of dice next to my desk. Look, I just rolled 1,1,1,3,3,4,5,5,6! The chance of this is 0.15%. Amazing! Except...anything I would have rolled would be amazing.

Likewise, the exact number of air molecules that enter your lungs in each breath is amazingly unlikely to happen, but it happens every breath.

So, the chance for you to exist was very, very low. But the chance for someone to exist was very high--it could have been any one of gazillions of people, but it just happens to be you. It's really no more interesting mathematically than that you might have just breathed in exactly 10,392,210,415,215,602,289,076 molecules of N2 in your last breath. That collection of molecules must be feeling awfully special right now. What was the chance for exactly them to be the special ones?

  • Your argument is very interesting... So you think it also applies in the case of questioning a probability of "becoming asymmetrically aware of universe", which feels somewhat qualitative question about the universe, and all your examples seems to be quantitative.
    – user2596
    Oct 27, 2012 at 10:08
  • @zplesivcak - I don't think the logic differs depending on whether you can write down the probability or only imagine that it is theoretically possible to write it down.
    – Rex Kerr
    Oct 27, 2012 at 10:12
  • "10,392,210,415,215,602,289,076" What kind of a giant do you think (s)he is? :P
    – Joe Z.
    Jan 29, 2013 at 4:35
  • @JoeZeng - An average human at sea level and at a comfortable temperature. Why--do you think my calculation is off?
    – Rex Kerr
    Jan 29, 2013 at 9:10
  • 1
    I forgot that we were talking about atoms, not body cells.
    – Joe Z.
    Jan 29, 2013 at 13:32

There are a related set of problems involving the Anthropic Principle:

The anthropic principle is the philosophical consideration that observations of the physical Universe must be compatible with the conscious life that observes it.

So, roughly, if you didn't exist and someone else did, it would be that other person marveling at the unlikelihood of their existence. Wikipedia has more.

Nick Bostrom is the philosopher most strongly associated (in my mind) with these investigations. Some interesting consequences are the doomsday argument and the sleeping beauty problem.

So roughly, I don't think the question you should ask is "how likely is it for me to exist?" but rather "how likely is it for someone like me to exist?"

If you ask the former, I think the answer is, as you say, "miraculous".

  • People would take the anthropic principle as evidence that there does lie something after death after all.
    – Joe Z.
    Jan 29, 2013 at 12:01

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