He was born in New Zealand. He became lecturer in philosophy at Canterbury University College in 1945, then Professor in 1953.
He became the John Locke lecturer in philosophy at the University of Oxford in 1966. From 1960 to 1966, he was a professor of philosophy at the University of Manchester. From 1966 until his death he was Fellow and Tutor in philosophy at Balliol College, Oxford.
He made contributions both to the history of logic and to modern formal techniques. A significant achievement was the foundation of tense logic. He also made important contributions to intensional logic, particularly in the influential posthumous work Objects of Thought.