Callinicos began his involvement with revolutionary politics as a student and his first writing for the International Socialists, organisational forerunners of the SWP, was an anlysis of the student movement of the period. He rapidly became known in socialist circles for his writings on Southern Africa, he has authored and edited a number of books on the region, and his interest in the then fashionable views of French philosopher Louis Althussar. For a Trotskyist such an interest in a thinker coming from a Stalinist tradition was unusual.
He was rapidly noted as a powerful writer and soon became a member of the Central Committee of the SWP, a position he has retained to this day. In recent years he has been responsible for the SWP's international work in which capacity he has presided over a number of major splits in the International Socialist Tendency's affiliated groups.