In the discussion of ethics, analogies and thought experiments are often used to support a certain viewpoint, or to test an ethical approach. A thought experiment often used to elucidate the difference between consequentialist (the ethicalness of an action is based on its ultimate end) and deontological (certain things [e.g. killing] are wrong, regardless of the situation) positions is the 'Trolley Problem'. I'll look at the original problem, and then at two interesting modulations of it.
The Original Trolley Problem
The dilemma goes like this: A train is heading full steam towards a two-way junction, and there's no time to engage the break. The train is currently set to run over 5 workers repairing the track, and there's no time to warn them. On the other arm of the track is a single worker.
You happen to be standing directly next to the lever that can be pulled to change the course of the train, killing the one worker instead of the five. What do you do? Which is the most ethical course of action?
The choice from consequentialism is clear: You must pull the lever for the greater good, saving five lives at the expense of one. However, an ardent proponent of duty-based ethics would most likely not pull the lever, as to change the course of the train would be equivalent to murder.
This raises some interesting issues and problems with both positions. While leaving the train to take its present course will result in the deaths of five people, changing the direction of the train (an act) will be certainly be equivalent to murder, even if it is for the greater good. Would leaving the train (an omission) be the same as murdering five people. This is the fundamental problem of acts and omissions, and whether there is any ethical distinction between the two. This is something that you will have a personal view on, mine being that there is no distinction between the two; if you are in a position of responsibility, to allow something to happen is equally bad as consciously doing something that will have the same effect.
The Bridge
One interesting change in the original problem is to have, instead of a single person on a branch of the track, a man on a bridge, that you can push off to save the lives of the five.
It's likely that this situation will have evoked a greater emotional response, even though both situations are essentially the same in terms of possible outcomes: Either five people will die, or one will die. Where does this difference come from?
One possibility is that, in the first instance, the death of the one person was intended (i.e. the train would not have run over the five people, even if there was no person on the other track). However, in this situation, the death of the single person is intended to save the lives of the five. This is the principle of 'double effect' - that while there are two results of the action (the death of the single person, and the survival of the five), in the original scenario the death of the one was unintended (but foreseen), while in the second the death was both intended and foreseen (to save the five).
Is there any difference between the situations? In terms of ultimate eventualities, no. However, there is still something that evokes a different response, and it is hard to put our finger on it. In part, it could be the simple fact that the death of the one person was unintended in the first, but intended in the second, as alluded to earlier. I believe that there may be something more to it though; that part of this is relating to the person in control of the situation.
People often give each other similar options between two undesirable events (would you rather do x or y?) Perhaps some of our opinions on the trolley problem stem from an empathising with the person who must make the decision. In the first situation, the person only needed to pull a lever to change the situation, simply changing the direction of the train. However, in the second, the person must physically push an unsuspecting person into the course of the train to stop it - a prospect that no one would like to face.
In summary, the distinction between the two scenarios comes from the nature of the act designed to avoid the worst eventuality. The difference comes, in my opinion, from the intuitive contrast between acts and omissions, and in part from our relating to the decision-maker. I've no doubt that you will have different opinions on the situations, and on whether there is any moral difference between them, and what the nature of this difference is.
The Surgeon's Dilemma
I will now present one final ethical dilemma. A surgeon has five patients who are all going to die within the week if they aren't given an organ transplant. Unfortunately, there are no suitable organs available for transplant, so are all certain to die very soon. However, there happens to be another healthy patient recovering in a nearby ward who happens to have all of the organs required.
I would be surprised if you were not very strongly against the killing of the healthy person, yet this situation is technically no different to that of pushing one person off the bridge to save five. There is, however, a few subtle difference that I think may be responsible for this disctinction.
The first is an intuitive 'slippery slope' argument - most people know that there is a shortfall in organs to be used in life- saving transplantation. If we assumed it ethical to kill the healthy patient to save the five, it follows that this should be done whenever the situation arises, hence leading to deaths of hundred, or thousands, of healthy people every year to satisfy demand. No person with any sense of morality would see this as a desirable state of affairs, so we naturally reject the original case.
The second is that, although the scenario specifies that a particular patient has the required organs, and that the five requiring the organs will die if they don't receive them in the next week, we may automatically think of other scenarios. Unlike the trolley scenarios, where there could only even be two options, the matter of organ transplantation has other options in the longer-term: Opt-out organ donation schemes, use of animal organs, transplantation from live donors (e.g. a kidney or lung), and even the harvesting of organs from the deceased who haven't given permission. In summary, the presence of better possibilities, even if not in this specific case, could also cause us to be outraged at the possibility of organ harvesting from the non-consenting living.
Daniel