studied law at the University of Amsterdam, where he completed his Ph.D in 1971. He has been professor of philosophy of law in at the University of Groningen and professor of international private law at the University of Amsterdam. He taught at the European University Institute in Florence from 1987 to 1993 and subsequently came back to Amsterdam to assume a chair in migration law. From 1996 to 2003 he was chairman of the Fonds voor de Letteren and since 1989 he is a member of the Academia Europea.