How do we judge whether an action is morally right or wrong? If an action is wrong, what reason does that give us not to do it? Why should we give such reasons priority over our other concerns and values? In What We Owe to Each Other, T. M. Scanlon offers new answers to these questions, as they apply to the central part of morality that concerns what we owe to each other. According to his contractualist view, thinking about right and wrong is thinking about what we do in terms that could be justified to others and that they could not reasonably reject. Here is a an excerpt from the book.

Attempts to explain how the fact that an action is wrong provides a reason not to do it face a difficult dilemma. Understood in one way, the answer is obvious: the reason not to do the action is just that it is wrong. But this is surely not the kind of answer that is wanted: it simply takes the reason-giving force of moral considerations for granted. Suppose, on the other hand, that we were to appeal to some clearly nonmoral reason, such as that people have reason to be morally good because, taking into account the effort that deception requires, the likelihood of being found out, and the costs of social ostracism, it is in their self-interest to be moral. This account might supply a reason for doing the right thing, but it would not be the kind of reason that we suppose a moral person first and foremost to be moved by. I will refer to this as Prichard’s dilemma. So a satisfactory answer to our question must not, on the one hand, merely say that the fact that an action is wrong is a reason not to do it; but it must, on the other hand, provide an account of the reason not to do it that we can see to be intimately connected with what it is to be wrong. Answers can thus be arrayed along one dimension according to their evident moral content, ranging from those that appeal to what seem most obviously to be moral considerations (thus running the risk of triviality) to those having the least connection with moral notions (thus running the risk of seeming to offer implausibly external incentives for being moral).

Explanations of the importance of morality and its reason-giving force can also be compared along another dimension, according to their degree of formality or, on the other hand, of substantive content. The strategy of formal explanations is to appeal to considerations that are as far as possible independent of the appeal of any particular ends. Kant’s theory is a leading example insofar as he undertakes to show that anyone who regards him- or herself as a rational agent is commit- ted to recognizing the authority of the Categorical Imperative. Habermas also appears to follow a formal strategy insofar as he argues that valid moral principles can be derived in argument following rules that must be presupposed by anyone who undertakes to engage in argument at all.

The alternative strategy is to explain the reason-giving force of moral judgments by characterizing more fully, in substantive terms, the particular form of value that we respond to in acting rightly and violate by doing what is wrong. The aim is to make clearer what this particular form of value is and to make its appeal more apparent. Alasdair MacIntyre has observed, for example, that the Christian version of Aristotelian morality gave morality a twofold point and purpose: to say what will lead to the attainment of man’s true end, and what is required by God’s law. These amount, in the terms I am using here, to two substantive accounts of the reason-giving force of morality. MacIntyre contrasts them with what he calls the Enlightenment project of grounding moral requirements in a conception of reason that dispenses both with the idea of divine authority and with that of a distinctive human telos. Insofar as it appeals only to a conception of rationality rather than to any specific good, this is an example of what I am calling a formal strategy. (I leave aside the question of whether this was the “Enlightenment project” and whether it is, as MacIntyre argues, unrealizable.)

Formal accounts have been attractive because it has seemed that the force and inescapability of the moral “must” would be well explained by showing that moral requirements are also requirements of rationality, and not dependent on the appeal of any particular good. But although showing this might provide the secure basis that some have sought for the demand that everyone must care about morality, it does not give a very satisfactory description of what is wrong with a person who fails to do so. The special force of moral requirements seems quite different from that of, say, principles of logic, even if both are, in some sense, “inescapable.” And the fault involved in failing to be moved by moral requirements does not seem to be a form of incoherence.

For these reasons, looking for a substantive account seems to me a more promising strategy. The main difficulty for such accounts is that it is not clear that they can give sufficiently strong answers to the questions of importance and priority. Once we identify one particular substantive value as the source of moral reasons it may be difficult to explain why that value should take precedence over all others, and why it is a value that, more than any other, everyone must recognize. This difficulty has not seemed insuperable, however, and in fact the accounts of morality that have drawn the widest support have generally been substantive ones. The ideas of God’s will and the human telos, for example, seemed to many to provide successful accounts of morality because they seemed to have the necessary priority and importance. (And there are of course many who think that if these beliefs are lost then no adequate basis for morality can be found.)

In our own time, the leading substantive account of moral motivation has been that offered by utilitarianism. In fact it seems to me that a large part of the appeal of utilitarianism lies in the fact that it identifies, in the idea of “the greatest happiness,” a substantive value which seems at the same time to be clearly connected to the content of morality and, when looked at from outside morality, to be something which is of obvious importance and value, capable of explaining the great importance that morality claims for itself.

Utilitarians’ objections to non-utilitarian accounts of morality, such as Bentham’s famous animadversions against rights, may seem to involve a claim to metaphysical superiority. Utilitarianism, it is claimed, bases morality on something undoubtedly real — human welfare. Rights and duties, on the other hand, seem to be mere ideas, without any foundation in reality. But the basic issue here is less a matter of metaphysical reality than one of reason-giving force. The familiar charge of “rule worship,” for example, derives its force from the presupposition that human welfare is something important and worth caring about and that rules (considered apart from any utilitarian foundation) are, by comparison, arbitrary. The plausibility of this presupposition makes the answering charge of “welfare worship” seem weak (even though there is, I believe, quite a lot to be said for it).

One problem with the utilitarian account is that the idea of the greatest happiness, despite its general moral significance, does not seem to be sufficiently closely linked to our ideas of right and wrong. Many acts are wrong even though they have little or no effect on people’s happiness, and the fact that an action would promote aggregate happiness does not guarantee that it is right. Moreover, even where happiness, or at least individual well-being, is clearly at stake, its appeal alone does not seem to account for the motivation we feel to do what is right and to avoid what is wrong. When, for example, I first read Peter Singer’s famous article on famine and felt the condemning force of his arguments, what I was moved by was not just the sense of how bad it was that people were starving in Bangladesh. What I felt, overwhelmingly, was the quite different sense that it was wrong for me not to aid them, given how easily I could do so. It is the particular reason-giving force of this idea of moral wrongness that we need to account for.

Mill’s view offers a way of responding to this problem. While he appeals to “the greatest happiness of the greatest number” to explain the importance of morality, he offers a separate account of how people are moved to act in the ways it requires and a separate account of the idea of moral wrongness.6 In chapter 5 of Utilitarianism Mill distinguishes between classifying actions as expedient or inexpedient (that is to say, as conducing or not conducing to the general happiness) and classifying them as right or wrong. “We do not call anything wrong,” he says, “unless we mean to imply that a person ought to be punished in some way for doing it; if not by law, by the opinion of his fellow creatures; if not by opinion, by the reproaches of his own conscience.”7 Mill seems to intend this as an account which captures most of what we ordinarily mean by right and wrong and interprets these notions as ones that he regards as normatively important (at least if the words ‘ought to be punished’ are understood in the light of the utilitarian formula, as meaning “the greatest happiness would be produced if they were to be punished”).

There is clearly something right about this account. Even on a nonutilitarian view, the idea that an action is of a kind that there is reason to have discouraged is surely not unrelated to the idea of its being wrong. The challenge is to formulate this relation correctly and to spell out how believing an act to be wrong is connected to seeing a reason not to perform it. The fact that it would be a good thing if people were discouraged from such actions by threat of legal punishment and social disapproval, or by an ingrained tendency to feel disapproval toward themselves, could provide a reason to acquire such a tendency, but that does not amount to a reason not to so act. What we need to do, then, is to explain more clearly how the idea that an act is wrong flows from the idea that there is an objection of a certain kind to people’s being allowed to perform such actions, and we need to do this in a way that makes clear how an act’s being wrong in the sense described can provide a reason not to do it.

Related: Read a New York Times Magazine feature on the key role of Scanlon’s book on the hit NBC sitcom, The Good Place.