Theo van Tijn (1927-1992) held the chair in economic and social history at Utrecht University from 1969 until 1992. Along with his scholarly work, he was very active in areas related to the historical profession, e.g., as an editor of the Tijdschrift voor Geschiedenis (1971-1981) and a member of the Board of the International Institute of Social History.
His political activities are less well known. In the autumn of 1945, Van Tijn, born and raised in a revolutionary-socialist milieu in Amsterdam, joined the Revolutionair Communistische Partij, the Dutch branch of the Fourth International, the latter having been established in 1938 by Trotsky.
When it became obvious that Dutch society would not undergo a process of radicalization – as had been generally expected after the second world war – the Trotskyites decided to join the social-democratic Partij van de Arbeid (PvdA) and build a leftist opposition inside this party.
To pursue this goal, in 1955 the Sociaal-Democratisch Centrum (SDC) in the PvdA was established as a platform for criticism directed against the imperious mentality of the party. Van Tijn edited the magazine of the SDC Socialistisch Perspectief until 1961. In 1959 the PvdA congress ruled that membership in the SDC was incompatible with party membership. The protest against this rule was negligible – a clear sign of the SDC's weakness. This proved to be the overture to Van Tijn's farewell to the Fourth International in 1961. However, the Cuban Revolution was the decisive factor. This revolution had achieved its goals without a Bolshevik revolutionary party, and to Van Tijn this clearly demonstrated the redundancy of the Fourth International.
In 2011 the IISH received a lively letter exchange about this farewell to the Fourth International between Van Tijn and Ernest Mandel, Marxist economist and member of the International Secretariat of the International. The correspondence is to be found in the papers of Theo van Tijn.