Mark writes to Juliet and says that he's obtained opera tickets from his music critic for that evening. Juliet agrees to go, but expresses sadness for the music critic. Mark says that the critic can watch from the standing room and write about the "uplifting effect of opera on the poor."
Mark's comment about his music critic again shows how little he cares for or respects others. He also encourages Juliet to think this way, suggesting that if they were to marry, he'd want her to share all of his thoughts.