The period beginning immediately after the Second World War, saw the appearance of artists from the Cobra movement, such as Asger Jorn (The three sages), La Jeune Peinture Belge and, later, lyrical abstract painters whose enthusiastic works are richly coloured.

With his paintings, Francis Bacon gives a good illustration of the indescribable (The pope with owls). The rapid multiplication of international relations and the trend towards European unification have meant that Belgian art is no longer able to be conceived outside the development of international art. Artists, and their works, are no longer very easy to catalogue. Is Potato chips in bags by Claes Oldenburg a painting or a sculpture? Pierre Alechinsky works in the indecisive area of the readable gesture and graphic drawing and sometimes the other way round. Does he belong to the Cobra movement or to the Paris School? It now seems to be just a matter of rhetoric because a great many interesting artists are proving themselves in their production of diversity that flagrantly contradicts the uniformity pre-supposed by a personal style. Neverthless, the limitation and uniformity of methods of expression enable us to make a very deep analysis of the aesthetic properties of images.

Hence with Dan Flavin ("Untitled, Jan. 22, 1964"), the immaterial nature of the light makes it possible to explore the ground between painting and sculpture. Lucio Fontana literally pierces the wall between representation and reality (Concetto spaziale. Attese). Marcel Broodthaers is known above all for works in which he attempts to transpose art into literary language. Yet a good part of his work is situated on the boundary between traditional objet d¹art and critical gesture (Triumph of the mussels II or Red Mussels in a cooking pot).