His work Thucydides Mythistoricus (1907) argued that Thucydides' History of the Peloponnesian War was informed by Thucydides' tragic view. He is probably better known now for his Microcosmographia Academica (1908), the classic insider's satire on academic politics. It is the source of a number of catchphrases, such as the doctrine of unripeness of time.
He married the poet Frances Darwin, daughter of Francis Darwin and granddaughter of Charles Darwin — she became known under her married name. They had 5 children: Christopher, Claire, Helena, Hugh, and the poet John Cornford.