"It just knows."
"That's not possible. A train doesn't know anything. It's just a train."
"The people driving the train know which track to take, okay? They switch tracks manually."
"Well, do you think a train knows where it's going anyway?"
"What? No. The people know. They're on a schedule."
"But what if the track won't move? How does the track know which way the train will go? There's no one driving the track."
"You're just being silly now. See that broom there? The train-person uses that to switch the track."
"Oh. What if the broom doesn't want to push the track?"
"Then I guess the train would stay on the other track."
"Then the train gets to decide where it's going after all? Or the broom decides?"
"Neither! No one decides anything! Do you have a point here?"