A great deal of ink has been spilled attempting to show that contractualism, alternately, can or cannot accommodate “numbers” in a plausible way. Contractualism aspires to provide an attractive and theoretically robust alternative to consequentialism and the unrestricted interpersonal aggregation that it implies (foundationally anyway), but the abiding worry about the contractualist approach to aggregation has been that it proves too much: while it rejects appealing to numbers in some cases where that rejection seems correct, it also rejects appealing to numbers where numbers seem clearly relevant or even dispositive. What I want to suggest here is a modestly deflationary way that contractualism might be able to accommodate the relevance of numbers.
Rahul Kumar and I are working on a paper together on contractualist risk imposition, and while a discussion of aggregation may not make the paper's final cut, I've been trying to figure out a way for a contractualist to consider population risk in addition to individual risk (i.e., the number of people who are subject to risk at any level, and not just the level of risk that any one person is subject to). This puzzle is of course just one instance of the wider challenge a contractualist has of dealing with interpersonal aggregation. So here's my proposal: interpersonal aggregation is morally permitted/required, according to contractualism, if but only if we first satisfy what we owe to each other. In the standard life-saving case, where one person is on the first rock and five are on the second and you can only rescue those clinging to a single rock, this proposal holds that an individual claim from each rock cancels out or silences the other, providing in particular the recognition that is owed to the single person on the first rock, at which point contractualist reasons run out/are fully satisfied, allowing non-contractualist (though not anti-contractualist) moral reasons about states of affairs or just general goodness to account for saving the greater number on the second rock. This, it seems to me, captures what is right about Scanlon’s and Kamm's and Kumar’s approaches to aggregation while also capturing what seems to be right about Raz's deflationary account of aggregation, revolving around reasons/values simpliciter. The claim of the one who ends up not being rescued matters but is met by a symmetrical reason, so that what we owe to each other has been satisfied, at which point we look to the fact that there are four people whose lives could be saved and the world accordingly made better if we rescue them.
This approach takes seriously Scanlon's claims about the limited moral domain that his theory covers. What we owe to each other remains the most important part of morality, but it is only one part. My proposal holds that what we owe to each other must be still satisfied, but it also recognizes that satisfying that is not always the last word on what to do all things considered, and that if contractualist reasons run out — as I think they do when symmetrical claims cancel out or silence each other — then we can appeal to the domain of non-contractualist moral considerations (whose existence Scanlon implicitly recognizes) to resolve the matter. On this picture, then, contractualism does not *itself* solve all problems of aggregation (though it will solve some, like the Transmitter Room case), nor should it be expected to. It just doesn’t stand in the way of interpersonal aggregation in those recalcitrant cases where it really seems that the numbers do matter. What we owe to each other will sometimes be dispositive in and of itself, but even when it is not, it will nevertheless constrain non-contractualist moral reasoning. This approach differs from Raz's more thorough-going deflationary account of aggregation because it accepts the primacy of contractualist reasoning about what we owe to each other, but it shares with Raz the idea that in certain cases (in my view but not Raz's, those where contractualism itself is indifferent) the numbers will matter just because we can have reason to do that which preserves more value.
This of course implies that certain aggregation cases are not purely questions of what we owe to each other, but that's an implication that I think we can live with. I for one don't actually have the intuition that we owe it, as a matter of narrow contractualist duty, to each in the larger set to save them qua members of the larger set. Of course I do think that we ought to save the larger number, but it seems to me that we can, as contractualists, unapologetically do precisely that — it just won't be required by what we owe to each other.
I'd be grateful for your thoughts.