Fred is driving a car down a deserted highway in the middle of the night. His friend Sam is in the passenger seat. Fred reaches down to pick up something he dropped, taking his eyes off the road ((or maybe he doesn’t know he’s driving)). When he lifts his gaze back to the road, a deer has appeared.
What should Fred do? What should Sam do?
Clearly Fred should make a measured jerk of the wheel and swerve out of the way of the deer and Sam should do nothing. If Fred doesn’t swerve out of the way, he is responsible for the resulting crash. If Sam yanks on the wheel causing the car to go out of control and slam into a guard rail, he’s responsible for making the crash much worse.
The deer in the road is ultimately the cause for the crash, but as a force of nature he can’t be blamed for it. It is the actions or inactions of the people in the car that determine culpability. Because their actions determine whether or not the crash occurs and its severity, their culpability may not limited to not preventing the crash but for making it worse.
Friedman and Swartz found that Fred was at fault for the crash because he didn’t swerve when he should have. Ohanian has conjectured and has found some support in the data for the idea that Sam is at fault for making the crash worse because he jerked on the wheel.
But in the historical example, didn’t Sam jerk the wheel again after the car hit the guard rail? Yes, but jerks on wheels can, by luck, right out-of-control cars. Luckily for Sam, Eggertsson has found this was the case in the historical example. In that case, a jerk on wheel in the right direction happened to be productive.
Notice this doesn’t mean wildly jerking the wheel and sending cars out of control is a good idea. Also, the lucky productivity of the second jerk on the wheel doesn’t mean the first wasn’t bad.