(b Antwerp, 24 Nov. 1886; d Paris, 5 Oct. 1965). Belgian sculptor, painter, architect, and writer on art, active mainly in France, one of the pioneers of a mathematical approach to abstract art. In 1917 he joined the De Stijl group and turned from the conventionally naturalistic style he had previously practised to abstract sculptures in which he applied the principles of Neo-Plasticism to three dimensions (Interrelation of Volumes, 1919, Tate, London). From 1919 to 1927 he lived in the French Riviera resort of Menton and then for the rest of his life in Paris, where he was a member of Cercle et Carré and one of the founders of Abstraction-Création. From 1928 he began to design ambitious (and unrealized) architectural projects, including a ‘Skyscraper City’ (1930), whose cubiform structure resembles that of his sculptures.