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.