Peter Turchin, author of the 2006 War and Peace and War, suggests that collapse is what happens when a society stops being able to deal with the strains caused by population growth, leading to inequality and strife. Turchin has been compared to Hari Seldon, science-fiction writer Isaac Asimov’s “psycho-historian”, who studies the past to statistically predict the future. He belongs to a new breed of scientific historian taking a big-data approach, and argues — controversially — that societal spasms are cyclic. This idea itself comes and goes: the ancient Greeks took the cyclic nature of history for granted, but it has been unfashionable since the Enlightenment. Today, we tend to have a linear concept of progress, in which life generally improves for most people over the long term. Works such as Turchin’s see this trend as superimposed on an inherent cyclicity in the evolution of societies.