In this paper I present a solution to Parfit’s Mere Addition Paradox that relies on moral actualism, the idea that the relative value of worlds is determined by the aggregated preferences of people in the actual world. I will then describe a normative theory, based on actualism, which solves various puzzles in population ethics. In particular, this theory explains ‘the asymmetry’: that is, why it is wrong, on the one hand, to create miserable people yet permissible, on the other hand, not to create happy people.