As these remarks show, Nussbaum does not question the idea that the problem areas she identifies for Rawls's theory concern issues of justice. But why should this be assumed? Nussbaum mentions the alternative view presented in Utilitarianism in which it is the promotion of well-being and the avoidance of suffering rather than any idea of justice that is fundamental--only to reject it as being obviously inferior to Rawls's Kantian approach. It is true that Utilitarianism has many problems, some of them insoluble. At the same time it does seem to me to have one large advantage over Rawls's approach, which is that it is not a reiteration of received opinion.
Rawls's method in moral theory is a process of "reflective equilibrium" that involves clarifying our moral intuitions and shaping them into a coherent whole. In its nature this method can do no more than turn the moral beliefs expressed in current opinion into something like a system. In contrast Utilitarianism appeals to features of the world that stand outside our moral beliefs, and that could compel us to revise them. In this respect Utilitarianism seems better equipped to deal with a number of difficult moral issues, particularly those arising in our relations with other animal species. Once again, Nussbaum is fully aware of this difficulty:
The whole idea of a justification that looks for a reflective equilibrium and uses the idea of overlapping consensus is an anthropocentric idea. The holism in ethics that Rawls and I share may be contested at this point by a reasonable Benthamite, who will insist that what justifies changes in our treatment of animals is not the coherence of a family of human theories and judgements, even bolstered by reasonable agreement and overlapping consensus; it is, instead, a fact utterly external to the human point of view, namely animal suffering.
I am not a disciple of Jeremy Bentham, but it was Bentham who observed that it is not whether animals can think that matters but that they can suffer. Those who oppose animal experimentation--as I do myself--do so not because it cannot be fitted comfortably into a theoretical reconstruction of prevailing moral attitudes but because they believe these attitudes to be defective. If Bentham had aimed only to systematize the moral beliefs of his day he would not have been one of the first Western thinkers to give animal suffering proper attention. With all its difficulties Utilitarianism allows a critical distance from received opinion that Rawls cannot provide.
The trouble with Rawls's theory is that it aims to stay on the surface of things and very largely succeeds. Instead of digging into the metaphysical and epistemological questions that have preoccupied philosophers in the past, Rawls seeks to avoid them. Its goal is not truth but agreement, which he believes can be achieved through a systematic reconstruction of current moral beliefs. But which moral beliefs are allowed into consideration, and how is this decided? As a method in moral theory, reflective equilibrium has the fatal flaw of intuitionism. It has no way of addressing those who stand outside the charmed circle of people whose intuitions are viewed as relevant.
As a way of doing political theory it is prone to a corresponding failure of realism. The data that are used to construct the theory of justice are the moral intuitions of the liberal academy, but these are no longer widely shared in the larger society (if they ever were) and have little leverage on political practice. Anti-liberal forces such as ethnic nationalism and religious fundamentalism have come to shape much of contemporary political life. Yet, like Rawls, Nussbaum barely mentions this fact. She notes that just institutions of the kind envisioned in Rawls's theory "do not come into being unless people want them, and they can cease to be if people stop wanting them, something that the demise of New Deal-style social democracy in the United States has shown all too clearly." She does not ask how the rights and liberties she believes ought to be enshrined in law can survive when the larger political culture is indifferent or hostile to the values they express.
In a curious convergence liberal theory has given up on politics at a time when liberal values have become marginal in practice. Instead of trying to understand the forces that shape political life--as John Stuart Mill did in his writings on socialism and nationality, for example--contemporary liberal thinkers have constructed a legalistic edifice from which politics has been excluded. Nussbaum is aware that this rickety structure shuts out a great deal that is important, and in Frontiers of Justice she tries to let in some light. If she achieves less than she might it is because the giant shadow of Rawls stands in her way.