Tuning In to Shomea Keone

Every Friday night, a host says Kiddush and everyone at the table fulfills the mitzvah just by listening. But what exactly is being credited to the listener: every word the host said, or only the result of his speaking? That question explains three disputes that look unrelated: Birkas Kohanim said out loud, saying "Haman's sons" in one breath on Purim, and answering Kedusha silently during the Amidah. It also explains why Rabbi Akiva Eger and the Rosh disagree about the Amen after Birkas HaGomel. Anyone who likes to see the logic behind the halachos will enjoy following it.