As for this conference, the third in something like a series, it seemed tome unimaginable, even excluded in advance. Last time, in 1992, when Didier Cahen alluded to its possibility in the attic on the last evening, asking me what the theme of a third conference would be, I still remem ber dismissing such a hypothesis: "This guy is crazy," I exclaimed. He wasn't so crazy, but the whole idea remains, like everything that happens, and such is the condition for something to be able to happen, impossible to anticipate. It is only after the event, reading the titles of these three meetings ("Les Fins de l'homme," "Le Passage des frontières," "I.:Animal