Why did Bill get on the bus? Because he wanted to visit his grandmother and knew the bus would take him there. No other answer will do. If he hated the sight of his grandmother, or if he knew the route had changed, his body would not be on that bus. For millennia this has been a paradox. Entities like “wanting to visit one’s grandmother” and “knowing the bus goes to Grandma’s house” are colorless, odorless, and tasteless. But at the same time they are causes of physical events, as potent as any billiard ball clacking into another.
