[...] These images, unreal, fixed, always alike, filling all my nights and days, differentiated this period in my life from those which had gone before it (and might easily have been confused with it by an observer who saw things only from without, that is to say who saw nothing), as in an opera a melodic theme introduces a novel atmosphere which one could never have suspected if one had done no more than read the libretto, still less if one had remained outside the theatre counting only the minutes as they passed. [...]