This post, at Crooked Timber, I think, reveals something quite interesting about appeals to equality. A conservative academic has apparently argued in favour of Bush's estate tax reforms, saying that because they apply equally to all, they are a form of equal treatment and egalitarian. This strikes me as true, but not in any interesting sense. All laws, which are non-arbitrarily applied, are egalitarian in the sense that they are applied equally to all. Indeed, all principles, which are non-arbitrarily applied, are egalitarian in this sense. What's interesting is what this might indicate about appeals to equality more generally, particularly, whether there is any sense in which an appeal to equality can be construed as anything more than a demand that laws and principles are applied non-arbitrarily, that like cases are treated alike, without the appeal becoming patently false. I don't think there is.
Consider the case of the poor. If at least part of what matters to us is equality, at least part of what is wrong with people being poor is that they are relatively badly off. To put it another way, what is morally offensive about people being poor is merely the fact that other people are rich. But this cannot be in the sense that the poor are deprived of something, because that would focus not on the relation of the poor to the rich, but on the status of the poor as poor, as not having enough. However, I am not sure in what other sense one might worry about the poor: surely what is morally offensive about people being poor is that they are poor, that they do not have enough to live well. This moral offence would be lessened in a society in which it would be less easy to rectify this situation, a society in which there were not rich people, whose goods could be partially redistributed to the poor in order to make them better off, but this merely shows that, to some extent, ought implies can: the wrong is, as it were, doubled in a society with rich people, because not only do the poor suffer, but, although something could be done, nothing is.
This kind of view may well lead to rough equality of outcome - because everyone has roughly similar generic human needs and purposes, everyone ought to recieve roughly the same amount of material resources, opportunities and so on - but it does not lead to equality of outcome because it in any interesting or important sense is an egalitarian view: although it treats like cases alike - the simple requirement of consistent and non-arbitrary treatment - it does not take equality, of itself, to a proper moral goal. This is because not only can we account for what most people take as egalitarian goals without invoking a value of equality, but invoking a value of equality leads to some deeply unpalatable conclusions. For example, even if equality is not our only goal, a world in which we are all totally blind is in some way better than a world in which 99% of people have perfect sight and 1% have partial sight, simply because it is more equal than a world in which everyone is better off, and the vast majority substanially better off. This 'levelling down objection' makes egalitarianism simply implausible.
Joseph Raz has also written rather well on the kinds of goods that go well with egalitarian distributive principles. Obviously, an egalitarian distributive principle has to have some set, and ranking of the members of that set, of goods over which it ranges, or else it would have to state that each and every unequal distribution was of equal moral concern, and the idea that my immense hoard of sand is as morally troubling, in non-bizarre situations, as my immense hoard of food, or political power, is frankly stupid. Raz argues that egalitarian distributive principles go with goods which are non-diminishing and insatiable - meaning that the goods in question are, regardless of how much one has, still a good, and regardless of how much one has, still a good to the same extent - because goods which are diminshing and satiable, by virtue of being diminishing and satiable, provide their own reasons for distribution.
For example, food is a diminshing and satiable good, because there comes a point at which more food is not a good: we are full, and eating more would make us ill. Equally, the hungry should be fed not because others have more food than them, but because they are hungry. It would make no sense to distribute food according to an egalitarian principle of distribution, because beyond a certain point, it is unnecessary and perhaps even wrong to give people more food, and below that point, people's desire and/or need for food provides us with reasons quite extraneous to how much food others have to give them food. The question then becomes whether there are any goods which are non-diminishing and insatiable. Raz argues there aren't, because goods which were truly non-diminishing and insatiable would have to be goods which themselves provided no reasons for their distribution: sand, for example, would be a non-diminishing and insatiable good, because it does not matter for whether any more is of any use to me how much sand I have. Unfortunately, this is because sand is not, intrinsically at least, a good at all. Indeed, it seems plausible that any good which did not, of itself, provide reasons for favouring one pattern of distribution over another, a good which was non-diminishing and insatiable, is not a true good at all.
All this, I think, makes any appeal to egalitarianism either pointless - what is being called for is equal treatment, which is simply a requirement of consistent and non-arbitrary application of principles or rules - or invalid - because egalitarian principles of distribution are not appropriate for any true goods. This does not lead to any substantive difference - other than on the levelling down cases - between my views and those of genuine egalitarians, but it is an important point, because one should be able to justify the policy position one takes, and if I am right, egalitarians cannot: either they are making the utterly banal point that whatever rules say, they should be applied, or they are making untenable claims.
Postscript: those interested enough to read academic literature about this should probably start with Frankfurt's 'Equality as a moral ideal' in his 'The importance of what we care about' - which also contains the essay on bullshit recently republished - Raz's 'Morality of Freedom', particularly chapter 9, and Parfit's 'Equality and priority', which was originally a Lindley Lecture, and also appears in the journal Ratio. There is also an unpublished article by Casal, 'Why sufficiency is not enough', attempting to defend egalitarianism.