Allocation of health care funds according to benefit/cost calculations (see previous post) cannot be expected to satisfy the person with the story about screening saving their life. Is there a different angle to approach the incommensurability of the individual experience and the net social benefit?

Puzzling over this I reconsidered the thought-experiment about a runaway trolley used in ethics and, more recently, neuroethics (http://en.wikipedia.org/wiki/Trolley_problem). As I remembered this thought experiment, six people were on a runway trolley headed for disaster (say, in the form of a gap in the tracks on a bridge over a ravine). You had a chance to switch them into a siding where the trolley would safely stop. There was, however, a person tied to the rails on that branch. One life would be lost to save the runway six. What would you do?

My answer has always been to reject the thought-experiment—it corresponds to a situation found nowhere in the real world and therefore tells us nothing about how people do or should think ethically. Yet, I now wonder if a variant of it might be helpful in relation to screening.

Notice first that the thought-experiment doesn’t need 6 people in the trolley; any ratio above one for the number of people on the trolley versus the number tied to the track puts you in the hypothetical ethical dilemma. Next, take the people out of the trolley and have them all tied to the tracks so the choice is between branches of the track—no fallen bridge over a ravine is needed. In fact, don’t have them tied to the tracks; simply have them crossing the tracks where a runaway trolley can hit and kill them. Now, instead of specific people, let us imagine a constant stream of pedestrians crossing the tracks in a place that makes them unaware of the approaching trolleys and unable to avoid it if it comes when they are crossing. Trolleys plural because runaway trolleys keep coming at random intervals on both tracks. The ethical dilemma is that you direct the pedestrians to cross one track or the other—which track do you choose for the pedestrians to cross?

Before you can see this as an ethical dilemma, you need to know some additional information. First, in the case of track A only, there is a pedestrian underpass. If this is not full when a pedestrian is sent to cross the tracks, they can go under the track. However, if a trolley goes overhead at that time, splinters come down and injure, not fatally, those in the underpass. So which track do you choose now that you know that track A means fewer fatalities, but more injuries.

Perhaps you choose track A. More likely you ask how often trolleys come, how often the underpass has room for more pedestrians, and the nature of the underpass injuries. Perhaps you decline to choose, leaving that up to the pedestrians once you pass on to them what you find out about the frequency of the trolleys, etc.

OK, but what do you say when I now tell you that there is a group P of pedestrians who have to cross track B. Why? Because there is a charge for the track A choice and they have no money. And before you say you want to subsidize them, I must tell you that the funds that might have gone for such subsidies have, at least up to now, been used to build more underpasses for track A. So what do you do now?

While you are mulling over that, let me supply another piece of additional information. There’s a group F who can afford the track A choice but are speedy track-crossers. That is, if they crossed track B, their fatality rate would be lower than average. Moreover, track A underpass capacity would be freed up so more for group P could take that choice free-of-charge. So what do you do now?

The final installment of this series will be explicit about how the new trolley scenario provides a different angle to approach the incommensurability of the individual experience and the net social benefit.