Mediation means that which stands, comes or moves between things otherwise separated or opposed. Serres’s work has never ceased to meditate upon mediation in every possible sense: as arbitration; moderation; mediocrity; passage; communication; combination; exchange; translation; transformation; substitution; surrogacy. Serres is fond of representing himself as a cross-over, an intermediary between worlds: a ‘middler’, to awaken from its sleep for a second a sixteenth-century word. More than a compendium or encyclopaedia of such forms, his work can be regarded as a kind of self-inventing machine for mediating between mediations.