Abstract
Population ethics studies the tradeoff between the total number of people who will ever live, and their quality of life. But widely accepted theories in modern cosmology say that spacetime is probably infinite. In this case, its population is also probably infinite, so the quantity/quality tradeoff of population ethics is no longer meaningful. Instead, we face the problem of how to ethically evaluate an infinite population of people dispersed throughout time and space. I argue that axiologies based on _spatiotemporal Cesàro average utility_ are the most appropriate way to make this evaluation, because their unique properties make them superior to other axiologies that have been proposed.