Who is left out when morality is a bargain?
I came to this question with a personal stake. I've used a wheelchair since I was fourteen.
The Hobbesian strand of contract theory says morality is what rational, self-interested people would agree to for mutual advantage. David Gauthier's Morals by Agreement (1986) is the most rigorous version I know. Its great attraction is that it doesn't require you to believe in anything spooky: it shows why even a selfish person has reason to keep agreements.
But a bargain needs parties who can help or harm each other. Gauthier was candid that beings who can neither contribute to nor threaten the cooperative scheme fall outside a morality built on mutual advantage. That includes animals, future generations, and some severely disabled people. Rawls was gentler, but his parties are imagined as fully cooperating members of society over a whole life, which leaves similar questions. Martha Nussbaum's Frontiers of Justice (2006) groups exactly these three gaps (disability, nationality, species) as the places where contract theory runs out.
So, an open question for anyone who takes the contract approach seriously: is this exclusion a defect in the theory, or is it correctly identifying the limits of one part of morality, with the rest supplied by something else, like sympathy or care? And if the latter, what is that something else, and why should anyone trust it to hold up when it's expensive?