Read the excerpt from "Hokusai's The Great Wave" by Neil MacGregor. In the early nineteenth century Japan had been effectively closed off from the world for 200 years. It had simply opted out of the community of nations. Kings are burning somewhere, Wheels are turning somewhere, Trains are being run, Wars are being won, Things are being done Somewhere out there, not here. Here we paint screens. Yes . . . the arrangement of the screens. This is Stephen Sondheim’s musical tableau of the secluded and calmly self-contained country in 1853, just before American gunships forced its harbours to open to the world. It is a witty caricature of the dreamy and aesthetic Japanese, serenely painting screens while across the seas Europe and America industrialize and political turmoil rages. What is the purpose of the outside source used in this excerpt?