A thorough analysis of alternate theories of societal collapse is followed by a presentation of the author’s own theory, with examples drawn from past collapses including the Roman Empire and the Mayan Empire. The book is at its best during the initial analysis of other theories, which come under rigorous scrutiny. Particularly entertaining are the author’s evisceration of “mystical” explanations (the people lost their vigor!).
The theory of collapse presented is centered around the notion of declining marginal returns on investment in complexity. Essentially, the author posits that societies become vulnerable to collapse when the returns on societal complexity decline or turn negative. And that in fact such “collapses”, rather than always being a disaster from the point of view of the people involved, represent a rational response to a situation where complexity is no longer providing returns that justify its costs, thus making a switch to a simpler society a better choice economically.
It’s an intriguing theory and the author uses four separate historical collapses to support it. Although a purely economic perspective on collapses surely leaves out important contributors to collapse, it nevertheless seems to shed significant light on the phenomenon.
The author also touches on the possibility that modern societies may collapse and largely dismisses it. The reason is simple: there are too many complex societies for any one to collapse, since another neighboring society would simply take over in resulting power vacuum. Perhaps!