Resumen: Miguel de Unamuno celebrates Don Quixote's madness as an affirmation of the “self”, in his Vida de don Quijote y Sancho. For G.K. Chesterton, the radical affirmation of the “self” is the main element in madness, but it is not something to be celebrated. For Chesterton, Don Quixote's madness is not so much in the affirmation of the “self” but in the affirmation of a forgotten reality, invisible for those who have become accustomed to live in a world gone mad: he is the only sane man in a crazy world. Elements of this reading of Don Quixote can be found, in spite of Unamuno, in his Vida de don Quijote y Sancho; it is Unamuno, more than Don Quixote who affirms his own “self” against reality.