“The masses, open and closed spaces, the lines, tones and colours can be organised in a parallel way. It is as though these relationships are built up in all their complexity to provide a vehicle for those things which cannot be objectively identified but which can nevertheless be expressed in this way” (Paul Moorhouse, ‘A Dialogue with Sensation: The Art of Bridget Riley’, in: Exh. Cat., London, Tate Britain, Bridget Riley, 2003, p. 23).