During World War II, he broke with his Roman catholic faith, and adopted moral values and an attitude of life based on stoicism. This became apparent in his first novel "Het boek van Joachim van Babylon" (The book of Joachim van Babylon), which was first published in 1947. From then on, he published a series of novels, such as "Goed en kwaad" (Good and evil, 1951), "Lament for Agnes" (1951), "De diaspora" (The Diaspora, 1961), "Zelfportret, gevleid natuurlijk" (Self-portrait, flattered of course) (1965) and "De parel der Diplomatie" (The Pearl of Diplomacy). In 1968, he wrote the theatre play "Helena op Itahaka". On his relation to Catholicism, he wrote "De afvallige" (The renegade) and "Biecht van een heiden" (Confession of a heathen), which were both published in 1971.