Abstract
"Nothing that is so, is so", says Feste. He says so ironically, talking to Sebastian, who he is convinced is actually Cesario. This is said for a specific situation, but it might actually be relevant for the whole play: Indeed, this apparently absurd quotation raises the question of illusion, which takes a big place in Twelfth Night. It highlights the paradox between appearance and reality. It can also be seen as the echo of another quotation by Feste, which is "that, that is, is". But Feste has not become crazy, he may even be wittier than we could expect because the answer to the question of illusion of theatre is probably between these two sentences. But to what extent? To what extent does illusion masters theatre? There is illusion at the level of the characters themselves (I) but also to the level of the audience (II), but it is probably not enough for the whole play to be summed up by illusion: illusion is only possible because the roots are real (III).
