Imagine that humanity has two possible futures ahead of it: Either we’re going to have a huge future like that, in which trillions of people ultimately exist, or we’re going to wipe ourselves out quite soon, thereby ensuring that only around 100 billion people ever get to live.

If there are eventually going to be 1,000 trillion humans, what should we think of the fact that we seemingly find ourselves so early in history? If the future will have many trillions of people, the odds of us appearing so strangely early are very low indeed.

If we accept the analogy, maybe we can be confident that humanity is at a high risk of extinction based on this so-called ‘doomsday argument‘ alone.

There are many critics of this theoretical ‘doomsday argument’, and it may be the case that it logically doesn’t work. This is why Ajeya Cotra — a senior research analyst at Open Philanthropy — spent time investigating it, with the goal of ultimately making better philanthropic grants.

In this conversation from 2021, Ajeya and Rob discuss both the doomsday argument and the challenge Open Phil faces striking a balance between taking big ideas seriously, and not going all in on philosophical arguments that may turn out to be barking up the wrong tree entirely.

Full transcript, related links, and summary of this interview

This episode first broadcast on the regular 80,000 Hours Podcast feed on January 19, 2021. Some related episodes include:

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#40 – Katja Grace on forecasting future technology & how much we should trust expert predictions.
#42 – Amanda Askell on moral empathy, the value of information & the ethics of infinity
#3 – Dario Amodei on OpenAI and how AI will change the world for good and ill
#41 – David Roodman on incarceration, geomagnetic storms, & becoming a world-class researcher
#10 – Dr Nick Beckstead on how to spend billions of dollars preventing human extinction
#62 – Paul Christiano on messaging the future, increasing compute, & how CO2 impacts your brain.

Series produced by Keiran Harris.

Six: Ajeya Cotra on worldview diversification and how big the future could be