Galor argues that the driving forces of human development override setbacks such as wars, pandemics and depressions to deliver ever-increasing prosperity and welfare. They will, he believes, continue to propel a "relentless march of humanity" towards an "even more bountiful future".

While the book makes some interesting points, you might have imagined that climate and ecological breakdown, as they present the greatest threat to the optimism that he professes, would be covered in depth. But while he acknowledges their importance, his treatment is remarkably brief, even glib. The only source he cites in support of his main contention on the issue is Bill Gates, whose techno-utopianism and political naivety are notorious among environmentalists. Instead of detailed analysis, I found handwaving and magical thinking. Galor claims, without providing the necessary evidence, that "the power of innovation accompanied by fertility decline" may allow us to avoid a difficult choice between economic growth and environmental protection. He asserts that a decline in fertility will buy us the time we need to develop unspecified "revolutionary technologies" that will one day rescue us from the climate crisis. So, rather than encouraging countries to adopt "clean energy technologies and environmental regulations", we should instead help them further to reduce fertility.

... A few days before his book was published in the UK, the UN Office for Disaster Risk Reduction warned that irrational optimism and a misperception of risk greatly exacerbate our exposure to disaster. The timing was coincidental, but it stands as a direct riposte to his claims. Groundless optimism could be seen as one of the "cultural traits" that, Galor says, help determine the journey of humanity. It leads us not to his "even more bountiful future", but to a different place altogether. His is the latest in a line of books by professional optimists – Gates, Steven Pinker, Matt Ridley – who have failed to grasp the nature of either Earth systems or the political economy that bears upon them. These men are not climate deniers; they are politics deniers. They appear to believe that the transformations necessary to prevent systemic collapse can happen without political pressure or political change. Understandably, the media loves them.