In the past twenty-five years, many philosophers have been persuaded by John Rawls that the root problem is that utilitarianism ignores “the separateness of persons.” So widespread is this contention, that it has become a virtual mantra.
William Shaw, Contemporary Ethics: Taking Account of Utilitarianism, Cambridge, Massachusetts, 1999, pp. 124-125
Another argument commonly used against aggregationism is also hard to understand (Rawls, A Theory of Justice, p. 27). This is the objection that utilitarianism “does not take seriously the distinction between persons”. To explain this objection: it is said that, if we claim that there is a duty to promote maximal preference satisfaction regardless of its distribution, we are treating a great interest of one as of less weight than the lesser interests of a great many, provided that the latter add up in aggregate to more than the former. For example, if I can save five patients moderate pain at the cost of not saving one patient severe pain, I should do so if the interests of the five in the relief of their pain is greater in aggregate than the interest of the one in the relief of his (or hers).
But to think in the way that utilitarians have to think about this kind of example is not to ignore the difference between persons. Why should anybody want to say this? Utilitarians are perfectly well aware that A, B and C in my example are different persons people. They are not blind. All they are doing is trying to do justice between the interests of these people. It is hard to see how else one could do this except by showing them all equal respect, and that, as we have seen, leads straight to aggregationism.
R. M. Hare, in Helga Kuhse and Peter Singer (eds.), A Companion to Bioethics, Oxford, 1998, p. 83
[I]f it is rational for me to choose the pain of a visit to the dentist in order to prevent the pain of a toothache, why is it not rational of me to choose a pain of Jones, similar to that of my visit to the dentist, if that is the only way in which I can prevent a pain, equal to that of my toothache, for Robinson?
J. J. C. Smart, ‘An Outline of a System of Utilitarian Ethics’, in J. J. C. Smart and Bernard Williams, Utilitarianism For and Against, Cambridge, 1973, p. 26