The Social Construction Of Disabilities
The example wrongly suggests that we can use a "Robinson Crusoe" test as the litmus test for distinguishing authentic disabilities from cases of purely socially constructed disadvantage. Take the example of deafness. According to the "Robinson Crusoe-test" deafness is an authentic disability: "Robinson Crusoe, alone on his island and unable to hear properly after a stroke, would still be disabled." Sound enough, but so what? The reason why a deaf Robinson Crusoe is disabled is that he lives in a very special social environment, an environment in which he cannot cooperate with other human beings. It would just be wrong to infer that, since deafness is an impairment to human flourishing in the Robinson Crusoe environment, then the disadvantages to which it leads in other environments are purely socially constructed.
I find the term "socially constructed" to be a problematic one, since it's so often mis-understood (and here I lay the blame on both over-enthusiastic proponents and lazy critics) to mean that something isn't really real. Perhaps a better way of thinking would be to think of advantages and disadvantages (in general, not just those typically treated under the heading of "disability") as being matches or mismatches between a person's capacities and qualities on the one hand, and the requirements imposed by their social and natural environment on the other. As Michele points out, everyone is always in a specific social and natural environment -- it's a fallacy to think there's some neutral environment or non-environment state in which we can judge a person's capacities and qualities.
Second, there's Shiva's post (via Ryan) about when suicide (assisted or otherwise) is justifiable:
If most depression is (and I do think most depression is) caused primarily by social conditions, then the obvious, non-medical solution to the problem is to change those social conditions (which, obviously, is easier said than done). However, if someone has truly endogenous depression (that is, in social model terms, their depression is not a result of disability, but is in fact their impairment), to the extent of unrelentingly feeling suicidal, and no drug treatment is successful in having a positive effect on it (as does happen in many cases), then is forcible suicide prevention - that is, denying death to someone who truly cannot find anything positive in life - really justifiable?
I basically agree with Shiva's position -- people have a right to choose to die, in implementing that right we need clear safeguards against pressuring people into exercising that right, when in doubt we should err on the side of life, and many of the things that lead people to feel suicidal are largely caused by their social environment. Where I would differ is in whether the question of endogenous versus social origins of a given person's suicidal desire is relevant to the justifiability of that person choosing suicide.
Things that are socially constructed are still real. A person who is suicidal for social reasons is still actually suicidal, and keeping them alive against their will is just as much a violation of their desires and a source of suffering as it would be if their suicidal wishes were caused by genetics. It may be possible to help such a person by changing the social conditions that cause their suicidal-ness -- but the fact is that such major social change is going to take a lot of time. Since the socially-suicidal person is suffering now, in our imperfect world, they have a right to give up and decide they don't want to wait around hoping for the revolution (I would say this is a general rule -- people have the right to cope with their problems in the here and now rather than martyring themselves waiting for major social changes to eliminate the source of their problems). Further, just because a person's suicidal desires have a social origin doesn't mean they can be fixed by social changes -- the effects of events in a person's life can have permanent impacts on their psyche (and body) that continue long after the cause is gone.
We should work to fix the social conditions that lead some people to become suicidal. But until we've completed that task, there will be socially-suicidal people popping up, who deserve the same choices as the endogenously-suicidal people who may always be with us.