Today, humanity is reaching new heights of scientific understanding—and at the same time appears to be losing its mind. Why do we find ourselves flooded with fake news, medical quackery, conspiracy theorizing, and “post-truth” rhetoric? Why do we fail to take advantage of the powerful tools of reasoning our best thinkers have discovered over the millennia: logic, critical thinking, probability, correlation and causation, and optimal ways to update our beliefs? And how does the rational pursuit of self-interest, sectarian solidarity, and uplifting mythology by individuals add up to crippling irrationality in a society? Join cognitive psychologist and popular science author Steven Pinker as he discusses why rationality matters, how it leads to better choices in our lives and in the public sphere, and how it is the ultimate driver of social justice and moral progress.