I think the claim that we basically understand the universe is misleading. I’m especially unconvinced by your vague explanation of consciousness; I don’t think we have anything close to an empirically supported mechanistic model that makes good predictions. I personally have significant uncertainty regarding what kinds of things can have subjective experiences, or why they do.
This also feels like a good opportunity to say that the Doomsday argument has never made much sense to me; it has always felt wrong to me to treat being “me” as a random sample of observers. I couldn’t be anyone except me. If the future has trillions of humans or no humans, the person which is me will feel the same way in either case. I can’t possibly condition on being me, because I couldn’t be anyone else. The doomsday argument treats my perspective as a random sample of all possible humans, or even all possible observers, which feels like a massive type error.
On a similar note, why is it remotely surprising that we live in a universe with laws of physics that support our existence? We couldn’t possibly observe any laws of physics except the ones we have. Does it even make sense to say that the laws of physics “could be different”? I’m not convinced we can even imagine a coherent universe with different fundamental laws of physics, in the same way that I can’t imagine what it would mean to live in a universe where the circle constant is something other than π. This may well just be a failure of my imagination, however – more crucially, hypothesizing that there are lots of universes with different laws of physics doesn’t actually explain why we observe our universe. This kind of multiverse idea is a strictly more complicated hypothesis than just accepting that our universe exists and being agnostic about others, right? The only remotely reasonable argument I’ve heard in favor of some kind of multiverse is that many-worlds is a simpler interpretation of quantum mechanics than wavefunction collapse. This is a distinct idea from the proposal that our universe was born as a random sample among countless others with different physical laws, which is not a simpler explanation of anything at all as far as I can tell.
If I have misunderstood or mischaracterized these arguments, please let me know.
Your objection against the Doomsday does not make much sense to me. The argument is simply based on the number of humans born to date (whether you are looking at it from your own perspective or not).
Okay, suppose I was born in Teenytown, a little village on the island nation of Nibblenest. The little one-room schoolhouse in Teenytown isn’t very advanced, so no one ever teaches me that there are billions of other people living in all the places I’ve never heard of. Now, I might think to myself, the world must be very small – surely, if there were billions of people living in millions of towns and cities besides Teenytown, it would be very unlikely to be born in Teenytown; therefore, Teenytown must be one of the only villages on Earth.
Clearly, this is absurd, right? The Doomsday argument says that if there are lots of other people in X scenario that is different from mine (be it living in the future or across the ocean), then it would be unlikely for me to experience not X, therefore those other people most likely don’t exist. But I am me, and I couldn’t be anyone else. It makes no sense to talk about the “probability of being me”. I don’t think it is possible to “assume I am a randomly sampled observer” or something like that.
The number of humans that I notice have been born to date does not depend whatsoever on how many humans might exist in the future. My experience looks exactly the same whether humanity will be deleted tomorrow by a rogue black hole or spend billions of years spreading across the universe.
It seems that your understanding of the Doomsday argument is not entirely correct—at least your village example doesn’t really capture the essence of the argument.
Here is a different analogy: Let’s imagine a marathon with an unknown number of participants. For the sake of argument, let’s assume it could be a small local event or a massive international competition with billions of runners. You’re trying to estimate the size of this marathon, and to assist you, the organizer picks a random runner and tells you how many participants are trailing behind them.
For example, if you’re told that there are only 10 runners behind the selected participant, it would be reasonable to conclude that this is likely not a marathon of billions. In such a large event, the odds of picking a runner with only 10 people behind them would be incredibly low. This logic also applies to the Doomsday Argument, whether you’re an outside observer or one of the ‘participants’. The key piece of information here is that you only know the number of individuals ‘behind’ you, which can be used to infer how likely it is that the total number of total ‘participants’ is more than X.
In the doomsday argument, we are the random runner. If the runner with only 10 people behind him assumed his position was randomly selected, and tried to estimate the total number of runners, he would be very wrong. We could very well be that runner near the back of the race; we weren’t randomly selected to be at the back, we just are, and the fact that there are ten people behind us doesn’t give us meaningful information about the total number of runners.
Humans alive today not being a random sample can be a valid objection against the Doomsday argument but not for the reasons that you are mentioning.
You seem to be suggesting something along the lines of “Given that I am at the beginning, I cannot possibly be somewhere else. Everyone who finds themselves in the position of the first humans has a 100% chance of being in that position”. However, for the Doomsday argument, your relative ranking among all humans is not the given variable but the unknown variable. Just because your ranking is fixed (you could not possibly be in any other position), does not mean that it is known and that we cannot make probabilistic statements about it.
I think the claim that we basically understand the universe is misleading. I’m especially unconvinced by your vague explanation of consciousness; I don’t think we have anything close to an empirically supported mechanistic model that makes good predictions. I personally have significant uncertainty regarding what kinds of things can have subjective experiences, or why they do.
This also feels like a good opportunity to say that the Doomsday argument has never made much sense to me; it has always felt wrong to me to treat being “me” as a random sample of observers. I couldn’t be anyone except me. If the future has trillions of humans or no humans, the person which is me will feel the same way in either case. I can’t possibly condition on being me, because I couldn’t be anyone else. The doomsday argument treats my perspective as a random sample of all possible humans, or even all possible observers, which feels like a massive type error.
On a similar note, why is it remotely surprising that we live in a universe with laws of physics that support our existence? We couldn’t possibly observe any laws of physics except the ones we have. Does it even make sense to say that the laws of physics “could be different”? I’m not convinced we can even imagine a coherent universe with different fundamental laws of physics, in the same way that I can’t imagine what it would mean to live in a universe where the circle constant is something other than π. This may well just be a failure of my imagination, however – more crucially, hypothesizing that there are lots of universes with different laws of physics doesn’t actually explain why we observe our universe. This kind of multiverse idea is a strictly more complicated hypothesis than just accepting that our universe exists and being agnostic about others, right? The only remotely reasonable argument I’ve heard in favor of some kind of multiverse is that many-worlds is a simpler interpretation of quantum mechanics than wavefunction collapse. This is a distinct idea from the proposal that our universe was born as a random sample among countless others with different physical laws, which is not a simpler explanation of anything at all as far as I can tell.
If I have misunderstood or mischaracterized these arguments, please let me know.
Your objection against the Doomsday does not make much sense to me. The argument is simply based on the number of humans born to date (whether you are looking at it from your own perspective or not).
Okay, suppose I was born in Teenytown, a little village on the island nation of Nibblenest. The little one-room schoolhouse in Teenytown isn’t very advanced, so no one ever teaches me that there are billions of other people living in all the places I’ve never heard of. Now, I might think to myself, the world must be very small – surely, if there were billions of people living in millions of towns and cities besides Teenytown, it would be very unlikely to be born in Teenytown; therefore, Teenytown must be one of the only villages on Earth.
Clearly, this is absurd, right? The Doomsday argument says that if there are lots of other people in X scenario that is different from mine (be it living in the future or across the ocean), then it would be unlikely for me to experience not X, therefore those other people most likely don’t exist. But I am me, and I couldn’t be anyone else. It makes no sense to talk about the “probability of being me”. I don’t think it is possible to “assume I am a randomly sampled observer” or something like that.
The number of humans that I notice have been born to date does not depend whatsoever on how many humans might exist in the future. My experience looks exactly the same whether humanity will be deleted tomorrow by a rogue black hole or spend billions of years spreading across the universe.
It seems that your understanding of the Doomsday argument is not entirely correct—at least your village example doesn’t really capture the essence of the argument.
Here is a different analogy: Let’s imagine a marathon with an unknown number of participants. For the sake of argument, let’s assume it could be a small local event or a massive international competition with billions of runners. You’re trying to estimate the size of this marathon, and to assist you, the organizer picks a random runner and tells you how many participants are trailing behind them.
For example, if you’re told that there are only 10 runners behind the selected participant, it would be reasonable to conclude that this is likely not a marathon of billions. In such a large event, the odds of picking a runner with only 10 people behind them would be incredibly low. This logic also applies to the Doomsday Argument, whether you’re an outside observer or one of the ‘participants’. The key piece of information here is that you only know the number of individuals ‘behind’ you, which can be used to infer how likely it is that the total number of total ‘participants’ is more than X.
In the doomsday argument, we are the random runner. If the runner with only 10 people behind him assumed his position was randomly selected, and tried to estimate the total number of runners, he would be very wrong. We could very well be that runner near the back of the race; we weren’t randomly selected to be at the back, we just are, and the fact that there are ten people behind us doesn’t give us meaningful information about the total number of runners.
Humans alive today not being a random sample can be a valid objection against the Doomsday argument but not for the reasons that you are mentioning.
You seem to be suggesting something along the lines of “Given that I am at the beginning, I cannot possibly be somewhere else. Everyone who finds themselves in the position of the first humans has a 100% chance of being in that position”. However, for the Doomsday argument, your relative ranking among all humans is not the given variable but the unknown variable. Just because your ranking is fixed (you could not possibly be in any other position), does not mean that it is known and that we cannot make probabilistic statements about it.