“It did not prevent a century of wars (many fought, notably, between people who spoke the same language). Instead, Esperanto’s speakers were persecuted throughout the 20th century.” (Stalinists thought they were spies; McCarthyists thought they were Commies.) “Esperanto may not have changed the world. But in both its ideals and its practice, it holds out the possibility of transforming the lives of the people who use it.”