In the 1950's Maurice Merleau-Ponty wrote an essay called "Le philosophe et son ombre'.¹ It was devoted to Husserl, and the title was well chosen for paying homage to a philosopher who so often spoke of the Abschattungen (shadings, profiles) through which perceived things present themselves to us. Shadows, of course, have a long and noble metaphorical history in philosophy; one might be put in mind of Plato's shadows which, unreal though they are, resemble and can lead us to the real entities which cast them. Merleau-Ponty had something else in mind, however: he linked the shadows cast by objects to the spaces between objects, and both in turn to what Heidegger called das Ungedachte in a thinker's work. Shadows, spaces, reflections, like the silences and pauses in and around segments of discourse, are not themselves objects or sentences. But they are openings and occasions for perceptions and thoughts which would not have been possible without them.