In his previous book, Steven Pinker documented the decline of violence throughout history. He now provides more ground for optimism, by showing that the world is steadily improving along several other dimensions that matter for human flourishing. His thesis is twofold: It comprises the descriptive claim that humanity’s lot is progressively improving, and the causal claim that this results from the operation of the enlightenment ideals of science, reason and humanism. The descriptive claim is well documented in the book. Pinker presents 70+ graphs showing that more humans are living lives that are longer, healthier, safer, more affluent, freer and with more resources to pursue meaningful lives than ever before. The causal claim – that the spread of enlightenment ideas drives this astonishing upward climb – is on a somewhat weaker footing. Pinker marshals no graphs or figures in its favor, but supports it with theory and compelling examples. In one sense, no more is needed, since it is obvious that, for example, the spread of science is a necessary condition for technological and medical progress. However, this is less interesting than Pinker’s stronger, and quite plausible, thesis that variation in enlightenment ideas accounts for most of the variation in human progress. To support this strong case for the efficacy of ideas, Pinker could have looked to recent attempts to rigorously identify causal effects of enlightenment ideas on development outcomes such as economic growth. The book discusses several challenges to continued progress, such as climate change and inequality, while arguing against doomsayers on each issue. In sum, Enlightenment Now is an impressive survey of evidence for the claim that humankind is doing better than ever before.