The ethics of existential risk concerns the questions of how bad an existential catastrophe would be, how good it is to reduce existential risk, precisely why those things are as bad or good as they are, and how this differs between different specific existential risks. There are a range of different perspectives on these questions, and these questions have implications for how much to prioritise reducing existential risk and which specific risks to prioritise reducing.

In the effective altruism community, the ethical perspective most associated with existential risk reduction is longtermism: existential risks are often seen as a pressing problem because of the astronomical amounts of value or disvalue potentially at stake over the course of the long-term future. But other ethical perspectives could also lead to a focus on existential risk reduction.

For example, in The Precipice (Ord 2020), Toby Ord discusses five different "moral foundations" for the importance of existential risk reduction:...

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