His work Thucydides Mythistoricus (1907) argued that Thucydides' History of the Peloponnesian War was informed by Thucydides' tragic view. From Religion to Philosophy: A Study in the Origins of Western Speculation (1912) sought out the deep religious and social categories and concepts that informed the achievements of the early Greek philosophers. He returned to this theme in Principium Sapientiae: The Origins of Greek Philosophical Thought (posthumously published, 1952). In some circles he may be better known 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 five children; Christopher, Clare, Helena, Hugh, and the poet John Cornford. Matthew Chapman is their grandson through Clare.