Evolution has permanently saddled our species with many irrational and destructive psychological traits, including revenge, dominance, nepotism, tribalism, lust, and magical and anecdotal thinking. It’s only institutions and norms that bring out the better angels of our nature that allow progress to be possible, and they face a Sisyphean struggle against our uglier instincts. What people call “optimism” is only an acknowledgment of the evidence that these institutions and norms have had some success.