What does Phoebe challenge Holden to do?

Phoebe demands that he name one thing he likes, just one thing, then stares at him, waiting for an answer. While she waits, Holden can’t keep his mind on the question at hand, and he starts thinking about James Castle, a boy who got bullied around at one of Holden’s old schools and ultimately jumped out of a window to his death. Phoebe interrupts his thoughts, now telling Holden, “‘You can’t even think of one thing.'” (pg. 171) Holden finally answers that he likes Allie and that he likes what he’s doing at the moment, sitting and chatting with Phoebe. Neither answer satisfies Holden’s sister, and she demands next to know what Holden’s going to do with his life. This question only leads Holden to another depressing rant about how most anything you do in the adult world ends up making a phony out of you. Finally, sitting on the bed, Holden comes up with one job he’d like to have. He tells Phoebe of a vision he’s had: “‘Anyway, I keep picturing all these little kids playing some game in this big field of rye and all. Thousands of little kids, and nobody’s around – nobody big, I mean – except me. And I’m standing on the edge of some crazy cliff. What I have to do, I have to catch everybody if they start to go over the cliff – I mean if they’re running and they don’t look where they’re going I have to come out from somewhere and catch them. That’s all I’d do all day. I’d just be the catcher in the rye and all.'”