In her daily English lesson, my daughter is currently reading The Hobbit. She isn't yet enjoying it so much, but because she wants to read Tolkien's trilogy, The Lord of the Rings (her interest having been piqued by the films), I've required her to first read The Hobbit.
Yesterday, she wanted to know why the ring turns people evil. That was getting ahead of the reading, but the question deserved an answer. So, I told her that the ring confers power on the one who possesses it and that people want power.
"Eventually," I told her, "the possessor of the ring becomes possessed by the ring."
"Why?" she asked.
"In the same way that we think that we possess things that may actually possess us," I explained -- which isn't precisely true in the story, but it was the best analogy that I could dredge up at the moment.
"What does that mean?" she asked.
"Well," I said, "suppose that you want some toy really badly, so you work hard for it, save your money to buy it, and then keep it just for your own use and not let anyone else play with it. Suppose you play with it all the time and no longer play with your friends."
"But I don't do that," she objected.
"Right," I agreed. "but you can imagine it, can't you? And if you were like that, wouldn't the toy possess you?"
She seemed to see my point. I left it at that, but there'll be more explaining to do when she realizes that the ring has a magical power of possessing its owner, not just a psychological one, and that the word "possess" is itself ambiguous.