It is common to hear about the problems of overpopulation, but do we really have too many people? Do we have an acceptable number? Or might we even have too few? Toby Ord shows how we ignore the good side of having a large population, how we can weigh the benefits and drawbacks of having a large population, and how future technologies could create a moral imperative to massively increase our population in the 21st century and beyond. Creative Commons Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales; http://creativecommons.org/licenses/by-nc-sa/2.0/uk/