Moral Luck: Part IV (and last)
Larry White offered one part of the answer. If every factor on which desert might be based, every characteristic of the individual, is due to some external cause for which that individual deserves neither credit nor blame, then we are all equally undeserving. If we all deserve nothing, any distribution of outcomes is equally just. If I don't deserve to be the particular person I am, don't deserve to be born in the country and century I was, I also don't deserve to be a human being rather than a rock–-and a rock has no claim to a per capita share of the national income.
Jadagul offered the other part. If you say "Adolf Hitler deserves to have bad things happen to him," your statement is about Hitler, not about the fertilized egg that would eventually become Hitler. If desert is applied to an actual human being, it is the characteristics of that human being that determine it–not the characteristics of the potential person, stripped of all accidental characteristics, that in some sense became that actual person. If I am hard working, honest and generous, the fertilized egg that became me, or the potential person that in some sense became that egg, doesn't deserve to have turned out that way. But I, having turned out that way, deserve to have good things happen to me.
I have discussed the question at such length for two different reasons. The first is that I find moral luck to be an interesting puzzle and paradox, only parts of which I can adequately explain away. The second is that, while I doubt there are many people who would be willing to accept the full blown version of radical egalitarianism sketched out in my previous post, the basic argument is an important element in the widespread view that equality of outcome is on the whole a good thing.
It is also an important element in views of criminal punishment. If criminals are not morally responsible for being the sort of people who commit crimes, then, arguably, punishing them for those crimes is unjust. If you believe punishment is unjust, you are likely to persuade yourself that it is also unnecessary--that crime ought to be dealt with by educating or reeducating people, rather than by punishing them. Few would carry the argument all the way, but I think it has a significant influence on what many people want to believe.