Robert Stein, The Borselen Affair and the Consolidation of Burgundian Power in the NetherlandsOver a period of barely three years, Philip the Good, duke of Burgundy, manifested himself as the most important prince of the Low Countries. In the years 1427-1430, he seized the principalities of Hainault, Holland, Zeeland, Brabant and Limburg, which he added to his extensive possessions in Flanders, Artois and Burgundy. In this same period, Philip acquired significant rights to the succession to Luxembourg, which eventually took place in 1444. In this way, he laid the foundation of the later unification of the Low Countries. These political achievements should not conceal the fact that the legitimacy of the Burgundian succession to these principalities was dubious. In November 1432, Philip arrested the mighty Zeeland nobleman Frank van Borselen. The present contribution argues that this arrest allowed Philip to legitimize his position as duke or count in the recently acquired principalities and thereby represents an important step in the consolidation of Burgundian power in the Low Countries.