A viewer to this channel recently asked me to provide my thoughts on The Doomsday Argument in
philosophy and if I thought there was any truth to it. The Doomsday Argument is an
increasingly popular probabilistic argument that indicates the human race is close to extinction.
So, first I’ll attempt to easily explain what the Doomsday Argument is
and outline why I think it is flawed. Although I think think it is wrong, there is something within
the Doomsday argument I think we should be wary of going forward which I’ll explain at the end.
The Doomsday Argument or DA was originally called
the Carter Catastrophe and proposed by astrophysicist Brandon Carter in 1983.
The argument caught the attention of philosopher John Leslie who helped champion it.
The modern form of the argument which I’ll go over has been formulated by Nick Bostrom.
DA is a probabilistic argument that claims to predict the number of future members of
the human species given an estimate of the total number of humans born so far.
It states all humans are born in random order and chances are any one human is born roughly in the
middle. Because you and I are most likely born in the middle of all humans to exist,
there is a decent chance the human race will become extinct in the next few centuries.
How’s that so? The argument goes roughly like this
Imagine I have two boxes In box A are balls with numbering 1-10.
In box B are balls numbering 1-100,000. Just imagine the boxes are roughly the same size for
this thought experiment and you can randomly pick any of the balls when you put your hand inside.
Say I blindfold you and put one of the boxes in front of you
and you draw a ball. If the ball has the number 5 on it, which box do you think it came from?
There’s a 1-10 chance it came from box A, and a 1-100,000 chance it came from box B.
So, most likely it came from box A, right?
Now imagine two scenarios for humanity, Doom Early and Doom Late. In scenario Doom Early,
the human race exists for another 100 billion people, a few more centuries, then dies out.
In Doom Late the human race continues to grow and expand across galaxies with
over 100 trillion humans being born thousands of years into the future.
To date, about 100 billion humans have been born. So according to the Doom Early scenario,
we exist somewhere in about in the middle of the human race.
In Doom Late, we’d be among the very first percentile humans to exist,
almost like drawing a #5 ball out of 100,000 total balls.
Because our birth rank is around 100 billion that’s we’re around the middle of the human race
and we’re here contemplating the DA argument, it’s more likely that Doon Soon is true. There
appears to be a 50% chance that the human race is going t’s going to end in the next few centuries
give or take for population stability, and we’re going to become extinct sooner rather than later.
Now some individuals challenge the specifics of the math and population in the argument
i.e. factoring into account decreases in birthrate, technology that could
radically extend human lives, and more that could affect the specific date of doomsday.
But, the general idea of the DA isn’t to give a specific date of doom. It’s
just that the human future is not so long and populous as we all like to think it will be
and that statistically, we’re more likely to go extinct than to leave
earth and colonize the galaxy for thousands of years to come.
So is the DA right and whether through wars, climate, the singularity,
or something else the humane race is set for extinction soon?
Well, I could be wrong, but I think the argument is flawed.
The issue has to do with faulty anthropic reasoning and the fact that we are not
typical observers. The anthropic principle states that we necessarily observe from
an environment and a universe capable of producing observers.
The anthropic principle has been used to help explain why this universe has the
age and the fundamental physical constants necessary to accommodate conscious life,
since if either had been different, we would not have been around to make observations.
But, instead of talking about environments, we’re talking about observers here.
Nick Bostrom calls this the self-sampling assumption - an observer should reason as
if they are randomly selected from the set of all existent observers in
their reference class (past, present, and future).
There’s this idea that we could have been any of the humans in existence,
but we happen to be randomly selected to this particular time in history which should then,
theoretically, give us clues about the future of the human race. We need to assume that we’re
typical observers for the DA argument to work.
But it’s one thing for a human to pluck balls out of a box with a fixed, certain number of
balls and make calculations, and another for a conscious entity to be ‘plucked’ from nonexistence
into a particular point in a reference class with an unknown total number of humans that will exist.
The problem is we don’t appear to be randomly selected in a way that gives each past,
present, and future human an equal chance.
Therefore, we aren’t typical observers rendering the argument fallacious.
For instance, it appears our existence isn't "randomly selected", but instead
“selected” by the year of our birth. We are necessarily alive at the time we consider our
position in human history, so everyone who is not alive now is excluded from the selection pool.
A person if truly randomly selected would be likely to live later
than right now if Doom Delay is true, meaning that we can’t assume we are randomly selected.
Plus, even if we could be legitimately treated
as a random selection with respect to birth rank, our position would always be relative
to the Doon Soon and Doon Delayed scenarios and the argument would still fail.
Both scenarios take the current time as the starting point for formulating the
probabilities with no possibility of the species becoming extinct before.
Think of it this way. Imagine our birth rank was
10,000 instead of around 100 billion and we understood the Doom Argument.
Using the data provided at that time in history, it would be around a 50% chance the humane race
would die out at around 20,000 birthmark and that it would be almost impossible for
the humane race to reach our actual birth rank in the billions, which is what we are.
Wherever we happen to be alive, the argument would be the same meaning our being alive
now can’t affect the probabilities of Doom Soon or Doom Delayed being true.
The doomsday argument is most likely incorrect due to the incorrect assumption that you are a random
sample from the set of all humans ever to have existed. It turns out we are not typical observers
which is required for the argument to work. Now you probably had an intuition that the
argument was wrong from the start and the important thing here isn’t disproving that
humanity may be going extinct soon. The more important thing is properly
understanding and using the anthropic principle. The anthropic principle is a relatively new
concept in philosophy and is being utilized more and more. It has helped win Nobel prizes in fact.
Although it can greatly help us, the anthropic principle when used incorrectly can lead to
shocking, seemly correct conclusions that are really incorrect. The popular simulation theory
is another one of these arguments that utilize the anthropic principle incorrectly I think,
but many people seem to think is right. We should be careful of the tendency to assume
that we, our environment, or observations, are truly typical or representative.