His thought experiments go something like this: Suppose that you and a friend are both up for the same job in another city. She interviewed last weekend, and your flight for the interview is this evening. Your car is in the shop, though, so your friend promises to drive you to the airport. But on the way, her car breaks down — the gas tank is leaking — so you miss your flight and don’t get the job.Would it make any sense to tell your friend, stranded at the side of the road, that she ought to drive you to the airport? The answer seems to be an obvious no (after all, she can’t drive you), and most philosophers treat this as all the confirmation they need for the principle.Suppose, however, that the situation is slightly different. What if your friend intentionally punctures her own gas tank to make sure that you miss the flight and she gets the job? In this case, it makes perfect sense to insist that your friend still has an obligation to drive you to the airport. In other words, we might indeed say that someone ought to do what she can’t — if we’re blaming her.