The ratchet metaphor was devised by Michael Tomasello and his colleagues in the field of evolutionary psychology. It describes a key contrast between human groups and groups of our nearest evolutionary relatives. Those species lack a uniquely human capacity that evolutionists have named: “shared intentionality.” It’s the ability to convey intricate subtlety of meaning from one group member to another.

Today, the shared meaning conveyed by the recorded and written word and by our national literacy level is our ratcheting device for achieving widely “shared intentionality” and for avoiding loss of acquired know-how from one generation to the next. It is the secret of group stability and progress.

Hirsch argues persuasively that in each nation of modern times the ratchet effect is the foundation of literacy, of technological improvement, and of emotional national unity. History and recent science combine to say that the ratchet effect must become an explicit progressive goal of modern schools and other national institutions.