Bion left a reputation which has grown steadily both in Britain and internationally. Some commentators consider that his writings are often gnomic and irritating, but never fail to stimulate. He defies categorisation as a follower of Klein or of Freud. While Bion is most well known outside of the psychoanalytic community for his work on group dynamics, the psychoanalytic conversation that explores his work is mainly concerned with his theory of thinking, and his model of the development of a capacity for thought.