Dans le Sophiste de Platon, un mysterieux etranger venu d'Elee entreprend de definir methodiquement le rival le plus farouche du philosophe, le sophiste. Sa definition est cependant interrompue par une tentative de refuter l'ontologie de Parmenide. La signification propre de cette refutation et sa relation exacte avec la chasse au sophiste demeurent tres controversees dans la litterature secondaire. Ce livre propose un commentaire suivi du dialogue montrant comment la distinction, souvent negligee, entre dialectique et apparences permet de trancher dans les controverses suscitees par le Sophiste, tout en restaurant l'unite et l'originalite profondes de la pensee de Platon. In Plato's Sophist, a mysterious Eleatic Stranger, the main character of the dialogue, undertakes a systematic definition of the philosopher's fiercest rival, the sophist. His hunt for a definition of the sophist, however, is interrupted by an attempt to refute the ontology of Parmenides. The philosophical significance of this refutation and its exact relationship to the sought-after definition remains a matter of great scholarly dispute. This book, by means of a running commentary on the dialogue, argues that the oft-neglected distinction between dialectic and appearances is not only the key to solving this and other exegetical conundrums, but also reveals the unity and originality of Plato's argument in the Sophist.