Picture Piece: Henri Bergson

You never look so good as when you've got an idea', drawls John Malkovich in Jane Campion's film adaptation of Henry James' novel The Portrait of a Lady (1996). Thought, the line suggests, has its own glittering allure: a visible reminder of the odd etymological affinity between grammar and glamour, between the dark rigour of reflection and its palpable presence as a seductive twinkle. Surely no image could ravish like a snapshot of the instant when a thought sparks into scintillating life?

The philosopher Henri Bergson, photographed in 1927 on the occasion of receiving the Nobel Prize for Literature, was unconvinced by the camera's capacity to arrest the flow of ideas. In his book Creative Evolution (1911) he posited our interior life as a stream of pure duration, a flux of time wholly at odds with the sclerotic pose of the photograph. The gravest philosophical error, he writes, is to imagine that we seize the world as a series of static tableaux, 'snapshots, as it were, of the passing reality'. Yet, here he submitted to the stiffest of studio scenographies, and was made to look like a little cartoon lightbulb-flash of philosophical insight. What can he be thinking?

If Plato's cave provides the original parable of the philosopher's distrust of images, later thinkers have learned to accommodate themselves to appearances, intuiting some enlightening link between the twin dark chambers of the mind and the camera. The trick is to be captured in action: photogenically engagé like the endlessly replicated milieu of Simone de Beauvoir, Jean-Paul Sartre and Albert Camus, or staring with the speculative intensity of the weirdly similar photographs of Ludwig Wittgenstein. Still, a certain iconography can freeze the philosopher into caricature, and it's best not to look too cute: Jacques Derrida's matinée-idol coiffure - which replicates the suave intricacies of his sentences - is a luxurious provocation to less presentable penseurs.

By contrast, Bergson has trussed himself into typology; he looks like a reputable dignitary documented by August Sander, or the sort of stiff personage collected and copied in Gerhard Richter's 48 Portraits (1971). But, skewered to the surface of the image by his tie pin, meekly perched atop the pedestal of his collar, he also looks a little mischievous, reminding us of his own definition of the comic (which could be a definition of the photograph): 'something mechanical grafted on to the human'. Perhaps this is his secret: despite his starched eminence, Bergson is trying hard not to laugh.