The present article analyses Seneca’s considerations on language and rhetoric contained in his Letters to Lucilius, written when the philosopher was old and retired from public life. So we can understand his defense of stylistic simplicity and the relationship established by him between language and government program, the proposal of the Letters to Lucilius is compared to texts from other Latin theoreticians, especially Cicero and Quintilian, who lived different political backgrounds, and who proposed rhetorical styles compatible to their historical and political viewpoints.