A primer on the Doomsday argument

Abstract

The Doomsday argument is a probabilistic argument that attempts to show that the probability that humanity will go extinct soon is much higher than generally believed. The argument follows simple and seemingly plausible premises, but it has faced scrutiny and challenges since its formulation. The argument proceeds in three steps: in the first, it establishes the self-sampling assumption, which states that observers should reason as if they were a random sample from the set of all observers. In the second step, using this assumption, it argues that the number of humans that will ever exist has a very low probability of being very large, based on the distribution of birth ranks. In the third step, the argument applies this conclusion to the present situation, suggesting that the probability of human extinction within a century is very high. Possible objections and alternative interpretations to the argument are also discussed – AI-generated abstract.