The Doomsday Argument

What is the Doomsday Argument?

The Doomsday Argument is a thought-provoking idea that tries to guess when humans might no longer exist based on math and the idea that we are probably not living in a very special time in human history. It’s like trying to figure out when a party will end based on knowing that you arrived at a pretty average time—not too early, not too late.

Here’s another way to think about it: Imagine you join a long line of people, but you don’t know if the line is going to get much longer. If you had to guess, you might think you are probably somewhere in the middle, rather than at the very front or the very back. The Doomsday Argument takes this idea and uses it to make a prediction about how many people will be born after us before humans are no longer around.

Key Arguments

  • The Copernican Principle: Believing that our time in human history is normal, not extraordinary in any way.
  • Bayesian probability reasoning: Changing what we think about how many humans there will be based on when we were born.
  • Anthropic Principle: This idea reminds us that we can only notice and think about the universe in a way that works with us being alive—a fact that can influence our guesses about human survival.
  • Random Sampling: This is like believing if you pick a pebble from a jar at random, you’re likely to grab one from the middle layer. If we apply this to when people are born, it means you’re more likely to be born in the middle of humanity’s time on Earth.

Key Examples Explained

  • If you’re told to guess the total count of a jar of marbles after drawing one out without looking, you’re more likely to guess a number that’s near the middle instead of near the top or bottom. This is like the Doomsday Argument because we’re using our ‘drawing position’ to guess the total.
  • Imagine you’re watching a random episode of a long TV show without knowing how many episodes there are. You might guess that you’re not watching the very first or the very last one just to play the odds. This is similar to how the Doomsday Argument uses our birth rank to guess our place in human history.
  • If a new type of candy is released in a limited series and you get one from the middle of the batch, it suggests that there are about as many candies made before as there will be after. This example connects to the Doomsday Argument because it deals with where we fall in a sequence.
  • When reading a book, if you open to a random page, you probably won’t be on the first or last page. It’s more likely you’ll open to one of the many pages in between. Like with the Doomsday Argument, it’s about guessing where we are within a total range.
  • If you join a queue at a theme park without sight of the front or end, it’s safe to guess you’re not the first or last. By finding your place roughly halfway, you get a sense of the queue’s length. Here, the Doomsday Argument uses similar logic to estimate humanity’s future.

Answer or Resolution

We don’t have a clear answer to whether the Doomsday Argument is right, because it’s more of a theory or a guess than something you can prove with facts or experiments. Whether you believe it or not depends on how you feel about the assumptions it makes and how it uses probability.

Major Criticism

One big criticism of the Doomsday Argument is its idea that we are typical or average observers in human history. Some people say there’s no strong reason to believe we’re in a normal place in time. Furthermore, people point out that this argument could change depending on who or what we include in our group of “humans,” which is known as the “reference class problem.”

Practical Applications

The Doomsday Argument doesn’t really come with a set of instructions for us to use in real life, but it can make us think differently about how we make decisions that affect our future. While not used for official planning or predictions, it can stir discussions about taking care of humanity for the long haul, instead of just focusing on what’s right in front of us.

Why is the Doomsday Argument Important?

Even if the Doomsday Argument doesn’t tell us exactly what will happen, it’s important because it challenges us to think about the survival of humans in a big-picture way. For example, if we take this argument seriously, it might push us to care more about protecting the environment or preventing wars that could wipe us out. It’s kind of like setting up a smoke alarm: you hope it never needs to be used, but it’s there to make you aware of the risk of fire.

For the average person, the Doomsday Argument serves as a reminder that our existence isn’t guaranteed and that our choices today have an impact on the future. It suggests that by understanding the risks of extinction, we can better appreciate our place in history and our responsibility to the next generations.

Related Topics

  • Existential Risk: This is thinking about events that could end human life or radically change life as we know it. Understanding the Doomsday Argument might make us take these risks more seriously.
  • Anthropic Reasoning: This involves using the fact that we exist to make guesses about the universe. The Doomsday Argument uses this kind of thinking when it talks about our place in human history.
  • Fermi Paradox: This is wondering why we haven’t found aliens when the universe is so huge. The Doomsday Argument is another way of grappling with big questions about life’s rarity and longevity.
  • Bayesian Statistics: A type of math that involves updating probabilities as you get new information. The Doomsday Argument is a famous, though controversial, application of this concept.


In summary, the Doomsday Argument takes a deep dive into probability and logic to offer a bold guess about how long humanity might be around. It’s not about foretelling the end of the world based on disasters or politics but about using our current position to predict the future. Although it’s not without its criticisms and limitations, its significance lies in sparking conversations about our survival and the thoughtful use of statistical reasoning. Overall, the Doomsday Argument stands as a profound piece in the puzzle of human existence and our ongoing quest to understand our place in the universe.