What does it mean to write "This is not a pipe" across a bluntly literal painting of a pipe?Rene Magritte's famous canvas provides the starting point for a delightful homage by French philosopher and historian Michel Foucault.Much better known for his incisive and mordant explorations of power and social exclusion, Foucault here assumes a more playful stance.By exploring the nuances and ambiguities of Magritte's visual critique of language, he finds the painter less removed than previously thought from the pioneers of modern abstraction.