Behaving rationally involves facing up to conditions of uncertainty; we never navigate the world with perfect confidence. Sometimes we are uncertain about the way the world is, but we can also be uncertain about our place within the world. This kind of situation arises in cosmology (where the relevant world can extend very far in space or time), and also in quantum mechanics (where new worlds might be created at any measurement), but also when we are simply unsure about the future history of humanity or whether we live in a computer simulation. I talk with philosopher Adam Elga about how to deal with these unique kinds of uncertainties.

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Blog post with transcript: https://www.preposterousuniverse.com/podcast/2026/02/23/345-adam-elga-on-being-rational-in-a-very-large-universe/

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Adam Elga received his Ph.D. in philosophy from MIT. He is currently a professor of philosophy at Princeton University. His research involves decision and game theory, epistemology, philosophy of probability, philosophy of mind, and philosophy of science.

345 | Adam Elga on Being Rational in a Very Large Universe

Sean Carroll's Mindscape: Science, Society, Philosophy, Culture, Arts, and Ideas