Recent painting exhibits reveal an expanded definition of painting. Though it does not appear to fit within the category of painting, Mel Bochner's 48&inches; Standards is included in this expanded definition. Clement Greenberg's modernist criticism attempted to limit painting to its formal elements, which led to the rejection of painting in minimalist and conceptual art movements. Mel Bochner integrates methodologies used by conceptual art to oppose modernist painting in order to open painting to theoretical discourse. In works such as 48&inches; Standards, Theory of Painting, and Theory of Boundaries, he brackets out the material signifiers that allow us to recognize painting in order to investigate its structure. In this way, painting acts as 'the missing signifier' in these works and place them firmly within the category of painting.