Government should have equal concern for the interests of all citizens, rather than playing favourites. I assume we can all accept this much. The question is how to interpret it. What does equal consideration require?
The obvious answer is provided by utilitarians: each person counts for one, and nobody counts for more than one. We should maximize utility without concern for its distribution. For suppose you preferred giving a slight benefit to the worst off over giving a larger benefit (in units of well-being, not merely resources, so never mind diminishing marginal utility) to someone already well-off. Then you are saying that the worse-off person counts for more. Even if they get a lesser benefit, that's somehow more important than a larger benefit for someone else. This is not giving equal consideration to all people. It is giving greater consideration to the worse-off. The name "prioritism" is apt indeed.
How might the egalitarian or prioritist respond? Egalitarians want everyone to be equally well-off. But that is quite different from giving equal consideration to the interests of all. It commits them to being quite unconcerned for the interests of the well-off. Improving the well-being of such people simply doesn't matter to them. Indeed, egalitarians (though not prioritists) might see such benefits as a positively bad thing, since it would increase the relative inequality. Egalitarianism asks that human well-being (utility) be diminished in the name of "fairness".
I guess that's the core difference then. Utilitarians see 'equal concern' as being a matter of avoiding bias, and of improving lives no matter whose life it is. Egalitarians, by contrast, see 'equal concern' in terms of fairness. Assuming that no-one is (initially) more deserving of well-being, the fact that some are already more well-off than others might suggest that the worse-off deserve to be compensated. This is a tricky issue which I hope to examine more in a future post.
(I'm not sure about libertarians and conservatives. I suspect they see it as a matter of avoiding explicit favouritism. But of course mere non-interference is not good enough if it implictly endorses favouritism. Such "equal (lack of) concern" is as worthless as the 'thin formal freedom' I keep complaining about. As it happens, many conservatives fail to live up to even this mediocre ideal, seeming to explicitly favour the rich!)
We might rephrase the core question as: who matters most? Here are some answers...
Utilitarian: "No-one! Everyone's interests have equal weight, so we should do whatever would best help the most people overall, no matter the resultant distribution."
Perfectionist: "The best! We should nurture excellence, so that humanity might achieve its potential. The import of this outweighs any suffering that may befall some along the way."
Prioritist: "The worst-off! The (negative) import of suffering outweighs the positive value of others' flourishing. We should focus on alleviating harm."
Egalitarian: "The worst-off! It's not fair that they should suffer while others flourish. We should remedy this inequality."
Libertarian: "Who cares? Just butt out and leave things as they are."
It's interesting to contrast the opposite weightings assigned by perfectionists and prioritists. I think that both are plausible to the extent that they conform, in practice, to utilitarianism. For example, due to Diminishing Marginal Utility, it is plausible that a more egalitarian distribution of resources would actually serve to maximize utility. But when considering, say, education, more good can be done by nurturing the growth of talented students than dull ones. (So giving priority to "special needs" students may not be what's best for society.)
Of course, it would be best if everyone could get all that they needed for a flourishing life. But sometimes we must make a choice, and are thus forced to ask "who matters most?" As you've no doubt noticed by now, I think that only utilitarianism genuinely shows equal concern for the interests of all. What do you think?
[P.S. I should note that this discussion relates to situations where no-one has any prior claim to special 'rights' or 'desert'. This helps us to avoid unnecessary complications.]