Pop quiz: is a nation its people—or its land? In other words, could you pick up everyone living in the United States, plop them down on Mars, and still call them Americans?
Mau might say yes. He says, "One person is nothing. Two people are a nation" (11.53). The people on the island come from all over the world, but they come together as one. You get the sense that, wherever Mau lived, he'd be the head of the Nation.
That's all very "We Are the World," but we learn at the end that the land matters, too. Mau's island is the birthplace of civilization as we know it. This knowledge changes the history of science as we know it, and might just bring the whole world together into one unified nation.
The word "nation" matters, too, because of an even bigger word: nationalism. In its friendliest terms, "nationalism" is simply the idea that people living in a particular nation are loyal and devoted to it. Americans love America; Swedes love Sweden; Indians love India. Pretty straightforward, right?
But nationalism has an ugly side. Nationalism can be used to make people think that their nation is superior to other nations or people—like, really, really superior. You know who really loved their nation? Nazis, and we all know what happened there.
Many nations are exclusive. They define themselves by who doesn't get to be included. The cool thing about Mau's Nation is that it's inclusive. Anyone who wants to can be part of the Nation—including, just maybe, the whole world.