This is what happens when you let philosophers have children. Zoë, as part of a multi-stage campaign to avoid going to sleep, asked me the other night, "What do 'safe' means?" Well, I explained (why do I let myself be drawn into these discussions?), when you're safe, nothing can hurt you. "Like tigers?" she asked. Right, like how here in the apartment you're safe from tigers, because they only live in the zoo and far away in the jungle, and there are bars on the doors and windows, and mommy and daddy are here. She pondered this for a moment. "You could still bonk your head." D'oh!