Imagine that you are being asked a question; a moral question involving an imaginary world. From the prior experience with people, you have learnt that people behave in a certain way; people are, for the most part, applied thinkers and whatever is your answer, it will become a cached thought that will be applied in the real world, should the situation arise. The whole rationale behind thinking of imaginary worlds may be to create cached thoughts.
Your answer probably won't stay segregated in the well defined imaginary world for any longer than it takes the person who asked the question to switch the topic; it is the real world consequences you should be most concerned about.
Given this, would it not be rational to perhaps miss the point but answer that sort of question in the real world way?
To give a specific example, consider this question from The Least Convenient Possible World :
You are a doctor in a small rural hospital. You have ten patients, each of whom is dying for the lack of a separate organ; that is, one person needs a heart transplant, another needs a lung transplant, another needs a kidney transplant, and so on. A traveller walks into the hospital, mentioning how he has no family and no one knows that he's there. All of his organs seem healthy. You realize that by killing this traveller and distributing his organs among your patients, you could save ten lives. Would this be moral or not?
First of all, note that the question is not abstract "If [you are absolutely certain that] the only way to save 10 innocent people is to kill 1 innocent person, is it moral to kill?" . There's a lot of details. We are even told that this 1 is a traveller, I am not exactly sure why but I would think that it references kin selection related instincts; the traveller has lower utility to the village than a resident.
In light of how people process answers to such detailed questions, and how the answers are incorporated into the thought patterns - which might end up used in the real world - is it not in fact most rational not to address that kind of question exactly as specified, but to point out that one of the patients could be taken apart for the best of other 9 ? And to point out the poor quality of life and life expectancy of the surviving patients?
Indeed, as a solution one could gather all the patients and let them discuss how they solve the problem; perhaps one will decide to be terminated, perhaps they will decide to draw straws, perhaps those with the worst prognosis will draw the straws. If they're comatose one could have a panel of 12 peers make the decision. There could easily be trillions of possible solutions to this not-so-abstract problem, and the trillions is not a figure of speech here. Privileging one solution is similar to privileging a hypothesis.
In this example, the utility of any villager can be higher to the doctor than of the traveller who will never return, and hence the doctor would opt to take apart the traveller for the spare parts, instead of picking one of the patients based on some cost-benefit metric and sacrificing that patient for the best of the others. The choice we're asked about turn out to be just one of the options, chosen selfishly; it is deep selfishness of the doctor that makes him realize that killing the traveller may be justified, but not realize the same about one of the patients, for the selfishness did bias his thought towards exploring one line of reasoning but not the other.
Of course one can say that I missed the point, and one can employ backward reasoning and tweak the example by stating that those people are aliens, and the traveller is totally histocompatible with each patient, but none of the patients are compatible with each other (that's how alien immune systems work: there are some rare mutant aliens whose tissues are not at all rejected by any other).
But to do so would be to completely lose the point of why we should expend mental effort to search for alternative solutions. Yes it is defensive thinking - what does it defend us from though? In this case it defends us from making a decision based on incomplete reasoning or a faulty model. All real world decisions are, too, made in imaginary worlds - in what we imagine the world to be.
Morality requires a sort of 'due process'; the good faith reasoning effort to find the best solution rather than the first solution that the selfish subroutines conveniently present for consideration; to explore the models for faults; to try and think outside the highly abbreviated version of the real world one might initially construct when considering the circumstances.
The imaginary world situation here is just an example; and so is the answer an example of reasoning that should be applied to such situations - the reasoning that strives to explore the solution space and test the model for accuracy.
Something else which is tangential to the main point of this article. If I had 10 differently broken cars and 1 working one, I wouldn't even think of taking apart the working one for spare parts, I'd take apart one of the broken ones for spare parts. Same would apply to e.g. having 11 children, 1 healthy, 10 in need of replacement of different organs. The option that one would be thinking of is to take the one that's least likely to survive, sacrifice for other 9; no one in their mind would even think of taking apart the healthy one unless there's very compelling prior reasons. This seem to be something that we would only consider for any time for a stranger. There may be hidden kin selection based cognitive biases that affect our moral reasoning.
edit: I don't know if it is OK to be editing published articles but I'm a bit of obsessively compulsive perfectionist and I plan on improving it for publishing it in lesswrong (edit: i mean not lesswrong discussion), so I am going to take liberty at improving some of the points but perhaps also removing the duplicate argumentation and cutting down the verbosity.
Well, look at how you had to arrive at this example. There had to have been an iteration with a traveller, and the example had to be adjusted to make it so that this traveller is an ideal donor for 10 people, none of whom is a good donor for remaining 9. We're down to probabilities easily below 10^-10 meaning 'not expected to ever have happened in the history of medicine'. (Whereas the number of worldwide cases when someone got killed for organs is easily in the tens thousands) Human immune system does not work so conveniently for your argument, so you'll have to drop the transplant example and come up with something else.
This should serve as quite effective demonstration of how extremely rare such circumstances are. So rare that you can not reason about them without aid of another person who strikes down your example repeatedly, forcing you to refine it. At same time, the cases whereby something like this is done for personal gain, and then are rationalized as selfless and altruistic - those are commonplace.
Privileging those exceedingly improbable situations to the same level of consideration as the much much more probable situations is a case of extreme bias.
The issue with rare situations is that the false positive rate can be dramatically larger than the rate of event actually happening, meaning that majority of detected events are false positives. When you carelessly increase the number of lives saved in your taking apart the traveller example, you are linearly increasing the gain but exponentially decreasing the probability of this bizzare histocompatibility coincidence.
If I heard that story from a doctor - I would think - what is the probability of this histocompatibility coincidence? Very very low. I am guessing below 1E-10 (likely well below). What is the probability that doctor is beginning to succumb to a mental disorder of some delusionary kind? Far larger, on order of 1/1000 to 1/10000 . Meaning that when you hear such story, there is still a very low probability still that it is true, and most likely explanation for the story is that doctor is simply nuts (and most likely he did just lie to you about the entire thing for sake of argument or something). Meaning that it would be (from utilitarian standpoint) more optimal to do nothing (based on belief that story was entirely made up) or call the police (based on belief that he did actually kill someone, or is planning to). [Of course I would try to estimate probabilities as reliably as I can before calling the police, to far greater degree of confidence than in an argument here.]
edit: a good example, the ambulance story here: http://lesswrong.com/lw/if/your_strength_as_a_rationalist/
Basically, the thought experiments like that - usually they are just a way of forcing a person to make a mistake when reasoning non-verbally, in the hope that he wouldn't be able to vocalize the mistake (or even realize he made one). In that case the mistake that the example tries to trick reader into is ignoring the error rate of the agent which is making the decision, in the circumstances where that rate is BY FAR (at least by 6 orders of magnitude I'd say, for the 10 patients) the dominating number in the utility equation.
Likewise the Chinese room tries to trick reader into making a 14 orders of magnitude error or so. Such mindbogglingly huge errors slip past reason. We are not accustomed to being this wrong.