In 2020, Oxford-based philosopher Toby Ord raised alarms with his book, “The Precipice,” where he estimated the probability of an “existential catastrophe” for humanity in the next century at one in six. This specific and alarming figure has sparked widespread debate among enthusiasts and skeptics alike, making headlines and influencing discussions on the risks humanity faces. In this article, we delve into the origins of this probability estimate, exploring the traditional and Bayesian perspectives on probability and examining the implications of subjective estimates.

The traditional view of probability, known as frequentism, relies on observations and repetitions. Think of rolling a fair die – the probability of landing a three is one in six based on the observed frequency of threes in a large number of rolls. However, when it comes to estimating the probability of human extinction, which is a one-off event, the lack of repetitions poses a challenge.

The Bayesian approach, named after statistician Thomas Bayes, focuses on ranking probabilities rather than relying solely on observations. Toby Ord’s book employs this perspective, presenting a table of potential extinction events with his personal estimates. These values, in a Bayesian sense, serve as relative ranks, suggesting the likelihood of different outcomes. However, the subjectivity of initial estimates (priors) and the scarcity of relevant observational evidence pose challenges.

Ord acknowledges the subjectivity of his estimates, emphasizing their purpose as indicators of the order of magnitude. Calibration, assessing the correctness of probability values, remains challenging without appropriate observational information. However, for public discourse and impact, the psychological resonance of a probability estimate can be more crucial than its calibration. In this context, “one in six” effectively conveys a sense of urgency without being dismissed as either negligible or excessively catastrophic.

While the accuracy of the “one in six” estimate may be difficult to ascertain, its psychological impact in public discourse is evident. As concerns about the future, including climate change and nuclear proliferation, demand attention, there’s a parallel need for widespread education on the nuanced understanding and careful use of probability. In navigating the complex landscape of potential existential threats, a balanced approach that considers both traditional and Bayesian perspectives can contribute to informed discussions about the risks facing humanity.