Philosophers have long sought to formulate a theory that explains the purposes of commonsense moral rules and provides principles enabling us to resolve the frequent moral dilemmas we encounter. Thomas Hobbes wrote that familiar moral rules are not relative to one culture or another but are “articles of peace,” necessary to civilized social life. It is in everyone’s rational self-interest to obey these rules; the grim alternative is a “state of war.” Immanuel Kant said that we have an unconditional duty to obey morality regardless of our desires and self- interests. His second “categorical imperative” says that we ought never treat others “merely as means,” but always as “ends in themselves.” To do so, we should follow a general principle that we believe everyone should follow in circumstances like our own.


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Derek Parfit, 1991

Kant held that his imperative justifies our commonsense duties to each other and provides a more fine-grained method of reasoning about what we ought to do when ordinary moral rules do not adequately address the complexities of life. For example, under what circumstances is it permissible to break a promise or deceive someone? To save innocent life or prevent great harm, surely, but not to benefit ourselves in minor ways; the hard cases lie in between.

In The Methods of Ethics (1874), among the greatest works in moral philosophy since Kant, the British philosopher Henry Sidgwick countered that the rules of commonsense morality coincide with utilitarianism. The “principle of utility” says that our actions are right and our laws are just to the degree that they promote the greatest sum of “utility,” or happiness, in the world. Happiness, Sidgwick says, is basically pleasurable experiences.

Contemporary utilitarians often identify happiness (now called “welfare” or “well-being”) with satisfaction of preferences, or of rationally informed desires. Until John Rawls’s influential social contract theory, expounded in A Theory of Justice (1971), utilitarianism remained the predominant moral theory in Anglo-American philosophy for over two hundred years. Utilitarianism remains highly influential among economists, in business and law schools, and in public policy institutes. In each it is common to hear arguments that a law or practice is justified because it improves overall well-being.

Utilitarianism is the most prominent example of a family of positions called “consequentialism.” These positions hold that actions, laws, or other conventions are right to the degree that they produce the best consequences, effectively “maximizing” the good. Many consequentialists today consider utilitarian general happiness only one of the good consequences that right conduct ought to promote. Some say that equalizing the distribution of happiness is also important. Some consequentialists endorse, as among the “intrinsic goods” that ought to be promoted, goods such as knowledge, creativity, aesthetic appreciation, love and friendship, or individual freedom.

Joining consequentialism and Kantianism is a third major position in contemporary moral philosophy, Harvard philosopher T.M. Scanlon’s “contractualism,” which reflects Rawls’s social contract theory of justice, the main influence on Scanlon. Rawls contends that justice requires that we act upon principles that would be unanimously agreed to among free persons equally situated behind an impartial “veil of ignorance” where they do not know particular facts that would bias their judgments.

Modifying Rawls’s social contract to apply it to personal duties, Scanlon’s contractualism says that we owe to each other a general duty to act on moral rules—such as not harming others and honoring our promises—that it would be unreasonable for anyone to reject. Contractualism resembles Kantian views in that it sees the morality of right and wrong as duties we owe to one another in recognition of our equal status as persons. In this respect, both stand together in opposition to consequentialist views, which construe right and wrong as derived from an impartial duty to promote the best overall states of affairs in the world, even if in the course of doing so what contractualists see as moral duties to persons may not be fulfilled.


Consequentialism, Kantianism, and contractualism are currently the three predominant positions in moral philosophy, and they are the primary subject of On What Matters, Derek Parfit’s enormous two-volume treatise.1 The book is divided into three main discussions: Part I, “Reasons,” argues for the objectivity of reasons for acting; Parts II–V are on the three main moral theories just mentioned; and Part VI, “Normativity,” defends the truth of moral and other normative judgments. There is also a helpful introduction by the book’s editor, Samuel Scheffler, and four critical commentaries by the philosophers Susan Wolf, Barbara Herman, Allen Wood, and Scanlon.

Parfit’s treatise is driven by two overarching concerns. First, he hopes to show that moral philosophy’s three predominant positions converge into a “Triple Theory.” Parfit’s Triple Theory says, first, that right and wrong are determined by moral rules that, when generally accepted, “optimize,” or promote the best overall consequences in the world. Though this sounds like a form of consequentialism—indeed Parfit calls it “Kantian rule consequentialism”—he offers both contractualist and Kantian arguments for it, appealing to the idea that the rules are ones that it would be unreasonable for anyone to reject, and that we all have reason to consent to them. Hence the designation “Triple Theory.”


Parfit’s second main concern is the truth and objectivity of morality and of reasons and values more generally. He argues that the statements we make about moral duties and valuable activities are not subjective or culturally relative, but are objectively true or false. Things are valuable, independent of whether we desire or value them. It is for Parfit an objective truth that happiness is good, suffering is bad, and that “no one could ever deserve to suffer.” If the reasons for moral and evaluative choices are objective and they justify true statements about duties and values, then moral and value relativism, subjectivism, and nihilism must be false. This is the main conclusion of Parts I and VI.

Parfit uses these two concerns to address the question of “what matters.” He discusses some of the things that ultimately matter—primarily happiness and an absence of human and nonhuman suffering. But he is especially concerned with showing that something must matter, independent of our subjective and culturally relative beliefs and desires. If there are no objective reasons or values but only desires and beliefs about what matters, then there are no truths about morality and what we ought to do. But then, Parfit contends, nothing can truly matter—regardless of how much we care about it—and we are condemned to nihilism. On What Matters dryly sets forth countless arguments, but its author is passionate in his conviction that there must be objective values that give meaning to our lives in a godless world. It is rare to find an academic philosophical treatise that sincerely grapples with such cosmic questions as “whether human history has been worth it,” given all the suffering that has existed in the world.


In Part I of On What Matters, “Reasons,” Parfit—challenging a fundamental premise of our consumer culture—denies that we have any reason at all to satisfy our own desires or preferences for their own sake. He argues the radical position that the mere fact that an action would promote the satisfaction of some desire is never in itself a reason for the person to do that action. People can and do desire most anything. For example, it’s conceivable, Parfit says, that a person could desire to be in agonizing pain. Surely this desire gives him no reason to satisfy it by putting his hand in the fire. In order for a person to have a reason to act as he desires, there must be some feature of the object of desire that makes it worth desiring. Practicing the piano in order to play better may be a goal worth desiring. Producing agonizing pain by burning your hand is not such a goal.

The position Parfit attacks here is known as “the desire-based theory of reasons.” It has enormous influence in philosophy, economics, political science, rational choice theory, and other academic disciplines. Underlying the desire-based theory is the premise that, in order for us to have a reason for doing anything, we must be motivated to act; and this requires a desire that propels our behavior. For our capacities for reasoning and intellect are, as David Hume said, “inert,” incapable of moving people to act in the absence of some desire, whether for wealth or knowledge or power or others’ happiness, for example.

The account of rationality implicit in economics and rational choice theory presupposes the desire-based theory of reasons for acting. In both, by definition it is rational for a person to maximize his individual utility: that is, to act to satisfy consistently ordered preferences for what he most wants. Parfit argues in effect that we have no reason to maximize our utility if we do so regardless of the objects of our desires. Whether we have reason to do what we most want depends, instead, upon the value of the objects of our desires, and the reasons these objects give us for acting. Pleasure, knowledge, love and friendship, aesthetic appreciation, justice and equality, and many other ends might be good reasons for acting and hence worthy of desire. But it’s these objective values themselves, and not the mere fact that we desire them, that provide us with reasons to pursue them.2

Economists may say they are insulated from these criticisms, since their task is to explain, not justify, individual and group behavior. We often talk about “the reasons” a person had for acting (e.g., Caesar’s reasons for crossing the Rubicon), referring to the beliefs and desires that cause conduct, with no moral or evaluative connotations. Parfit and other critics recognize this causal usage. What they object to is the subtle transition from a causal to a normative use of “reason for acting,” which implies what people ought to do. Economists and rational choice theorists, wittingly or not, make this transition when they say that a person acts “irrationally” by not maximizing his individual utility.


Parfit’s position implies that we often do not have sufficient reasons to act rationally by maximizing our own utility; and that acting nonrationally (if not irrationally) by refusing to satisfy certain utility-maximizing preferences (e.g., to steal, or cheat on taxes, knowing we will not be discovered) can be the best course of action. If Parfit is right, then ambitious economists perhaps should abandon their claim that economics is a “science of rational choice” and instead entitle it the “science of consistent, self-interested choice.”


It is difficult to understand Kant’s second categorical imperative, that we are never to treat others “merely as means” but always as “ends in themselves,” when that imperative is isolated from the rest of Kant’s moral philosophy. Parfit nonetheless tries. He simplifies his task by focusing exclusively on treating others “merely as means,” disregarding the idea of treating persons as ends. Clearly Kant cannot mean we should never rely on others as means to achieve our purposes; for it would be hard to make it through life without the services of strangers (grocers, physicians, teachers, garbage collectors, etc.). But instrumentally relying upon others is different from treating them merely as means, with no regard for their rights and interests—as if they were slaves. To rob someone at gunpoint, or transplant her kidneys without her consent, is to treat her merely as a means. Parfit suggests, however, that even when we harm others, we do not treat them merely as means if we deprive them of no more than is necessary to prevent a greater harm to someone else. Suppose you sacrifice a person’s leg to save another’s life, while refraining from sacrificing his second leg to save your computer. Since the victim’s well-being is considered and is sacrificed only for a greater good, it cannot be said that the victim is treated “merely as a means.”


The Granger Collection

Henry Sidgwick

This is an unusual interpretation of Kant. His second categorical imperative is usually regarded as a statement of the Enlightenment idea that persons, regardless of their social, religious, or ethnic status, deserve moral consideration and a fundamental level of respect simply by virtue of being persons. The traditional interpretation of Kant’s principle is that to treat others as ends requires that we respect certain moral rights that prevent their interests from being sacrificed even for the sake of creating greater overall good. This crucial element is abandoned in Parfit’s interpretation, since he regards the imperative as a prohibition against treating others “merely as means,” a prohibition that can be satisfied simply by taking their interests into consideration, even if we do not protect them.

The price of Parfit’s revisionist reading is that we lose any focus on certain fundamental ideas driving Kant’s moral philosophy. Kant saw everyone as having an “innate right to freedom,” including the “independence from being constrained by another’s choice.” This moral right is a direct consequence of the importance Kant assigns to individual autonomy, and to respect for others as ends in themselves. Since Parfit gives these core ideas little attention, individual rights occupy a secondary position in his “Kantian consequentialism.” Parfit’s primary concern is promoting individual well-being. The rights and freedoms people have are regarded as instrumental measures for promoting greater overall well-being and its appropriate distribution among people. As Parfit’s commentators argue, this is far from Kant’s own position; it also risks deflecting attention from the need to protect human rights.


Parfit argues that Kant’s first categorical imperative is more important. It says we should act only on a “maxim” or rule that we could will to become a “universal law” that is accepted and acted upon by everyone. After examining many possible interpretations of what Kant meant, Parfit formulates a principle that makes sense to him: “Everyone ought to follow the principles whose universal acceptance everyone could rationally will.” This is the “supreme principle of morality” Kant must have intended, and Parfit endorses it.

Parfit calls this principle “Kantian Contractualism.” It resembles, he says, T.M. Scanlon’s contractualism, which he summarizes as “everyone ought to follow the principles that no one could reasonably reject.” Neither version of contractualism tells us specifically which principles of conduct we ought to endorse; instead both provide procedures for thinking about the substantive principles of conduct we should observe. Applying these procedures in his own peculiar way, Parfit argues that both Kantian and Scanlonian contractualism justify “Kantian Rule Consequentialism”—his own phrase—which says, “everyone ought to follow the principles whose universal acceptance would make things go best.”

The assertion that we ought to do what is best may seem a commonplace moral platitude. But in moral philosophy, this expression has a specific meaning: that we should do what best promotes good consequences impartially construed, or that are, as Parfit puts it, “optimific.” This word refers to the consequentialist principle that right conduct is purely instrumental, aimed at achieving and maximizing, or “optimizing,” good consequences. Morality is then a kind of efficiency in promoting universal good. What is ultimately good is understood as states of affairs describable without moral concepts about what is right or just. Thus utilitarians say the happiness of humantity, or even all sentient beings, is ultimately good, whereas perfectionists such as Aristotle and Nietzsche say that what is good is achieving excellences of culture and of character.

Understood this way, Parfit’s claim that both Kant and contractualism require that we do what is “optimific” or “impartially best” is highly controversial. Scanlon for example denies it is true of his contractualism. Most philosophers regard Kantianism and contractualism as the primary alternatives to consequentialism. Parfit contends that Kantians, contractualists, and consequentialists are all “climbing the same mountain on different sides.” They are all, he says, committed to the Triple Theory: “An act is wrong just when such acts are disallowed by the principles that are optimific, uniquely universally willable, and not reasonably rejectable.” This is, for Parfit, the supreme principle of morality, the fundamental ground of our moral duties, and the ultimate test of the morality and justice of all we do.

Like some other sweeping positions, Parfit’s Triple Theory aims to neutralize its adversaries. Sidgwick, the main influence on Parfit, also surveyed the then-leading “methods of ethics” and argued that, suitably pruned, the more reasonable positions (intuitionism, perfectionism, Kant, and commonsense morality) all converge upon the doctrine of “universal hedonism” (Sidgwick’s name for utilitarianism). Subsequent utilitarians follow Sidgwick’s strategy, but none so inventively as Parfit. Parfit’s approach to Kant is far more sympathetic and sophisticated. Though, as I have suggested, he may have misconstrued or rejected fundamental features of Kant’s view—autonomy, respect for persons as ends, and the innate right of freedom—Parfit’s consequentialist interpretation of the categorical imperative will stimulate philosophers for years to come.


To test our moral intuitions and ultimately to show that it is always right to act on principles that maximize good consequences, Parfit relentlessly applies different versions of the so-called “Trolley Problem” and similar thought experiments that occupy many discussions in moral philosophy. The simplest version of the Trolley Problem asks whether it is permissible to throw a switch that redirects a runaway train in order to save five persons standing on a track, even though you know that one person on the other track will be killed as a result. This is Parfit’s “Tunnel” example. Many believe this is morally permissible, even though it causes another’s death. But what about pushing a large man off a bridge to trigger a train’s automatic brake in order to save five people? (Parfit calls this “Bridge.”) Most people think this would be wrong. But how is it morally different?

One difference Parfit mentions is that in Bridge, by pushing the man we directly cause a person’s death as an indispensable means to save five others—his body is the instrument we use to save them. By contrast, in Tunnel the death we cause by switching tracks is not instrumental to saving the five, but an unfortunate albeit “foreseen side-effect”—unlike Bridge it would be better were the individual who dies in Tunnel not on the scene at all. Act-consequentialists reject this distinction and contend that there is no moral difference; for the results are the same and all that matters in every instance is saving as many lives as we can.

Parfit rejects act-consequentialism. It implies, in the example he calls “Transplant,” that a physician should secretly kill his own patient in order to transplant his organs to save five others. According to Kantian and Scanlon’s contractualism, no one can rationally choose or agree to live in a world where physicians can kill their patients as a means of saving more lives, since this would undermine trust and the personal nature of the physician–patient relationship. Parfit accepts this conclusion, but still, in nonmedical emergencies involving no personal relationships, such as Bridge and Tunnel, he appears to affirm a more limited version of the consequentialist principle that everyone is permitted to do whatever saves the most lives.

Trolley-like examples are subject to endless variations. Suppose that in Tunnel the person who dies if we hit the switch is a healthy ten-year-old who has been tied down by five habitual child-killers on the other track who will be saved by our action. This added information would make a difference to most people, though perhaps not to Parfit. He thinks that bad people, even though they may be restrained or imprisoned to prevent harms to others, nonetheless should not suffer for their wrongs, since people are not free or “responsible for their acts in some desert-implying way” (i.e., in a way that implies that they deserve to suffer or die for their wrongs).

Susan Wolf comments that there is no single principle underlying our moral intuitions in Trolley cases. Allen Wood says unrealistic Trolley-like thought experiments are “worse than useless for moral philosophy,” since they (at least in Parfit’s use of them) leave out crucial information—including individuals’ rights, wrongs, and entitlements—and presuppose that all that matters is the number of lives saved or goodness and badness of states of affairs. Yet as Scheffler says, Parfit relies heavily on these examples to defend his book’s most crucial conclusion: that Kantian contractualism justifies rule consequentialism—to repeat, “everyone ought to follow the principles whose universal acceptance would make things go best.” If Parfit’s commentators are correct, and nothing he says refutes them, it’s doubtful that Trolley-like thought experiments tell us much about the general moral principles we should observe.


Most people believe that we normally ought to keep our promises, that parents have a duty to care for their children, and that we should not kill people simply because it’s advantageous. Are these statements objectively true independent of custom and our subjective attitudes? Many people, including philosophers, would deny that moral judgments can be objectively true. They might say that although moral duties are very important, they are expressions of our emotions, or depict social conventions, or, as Karl Marx argued, are ideological illusions obscuring class privileges. Part VI of On What Matters, “Normativity,” is a long defense of the objectivity of moral and other normative concepts and judgments.

Parfit argues that there are true normative statements about our moral duties and the values worth pursuing in life. The only alternative he sees is nihilism. If there were not such truths, “nothing would matter, and there would not be better or worse ways to live.” Parfit addresses the metaphysical objection that there can be no moral truths since truth then would have to depend upon the existence of mysterious moral facts that have no basis in nature. He argues that normative statements about values and our duties are true by virtue of the objective reasons that support them, and that there are objective reasons in the same way that there are numbers. In order for “2+2=4” to be true, numbers must exist in some sense, but we needn’t suppose that they are mysterious entities that exist either in nature or in a non-natural world. The same is true of moral and evaluative reasons.

Parfit concludes with an extraordinary chapter on Nietzsche. Nietzsche argued that morality died with the supposed source of morality’s commands (God), and that there is no value except what we create by willing it. Parfit replies that no one (including God) can make something right or good by commanding or willing it so. “Nor can we make anything matter.” Things matter because there are objective reasons independent of our will, choices, and desires, and these reasons justify moral and evaluative truths. Nietzsche’s attempt to overcome nihilism by grounding value in our choices about how to live, or in the “will to power” and commands of a Superman, failed (Parfit says), because arbitrary choices made without objective reasons cannot make something matter or create value.


In spite of its 1,400 pages, Parfit’s book does not adequately address two crucial questions. First, why should we regard morality and justice as maximization of impersonally good states of affairs? Second, what is the ultimate good that moral conduct is to maximize?

Sidgwick provides an answer to the first question. He says it is “a primary intuition of reason” that it is “‘right’ and ‘reasonable’” to do what is “ultimately conducive to universal Good or Happiness.” Sidgwick also says that it is a “self-evident principle that the good of any one individual is of no more importance, from the point of view (if I may say so) of the Universe, than the good of any other.” Parfit approvingly calls this the “Axiom of Personal Impartiality.”

It takes a refined philosophical sensibility to conceive of morality as a set of rules that maximally promote impersonally good states of affairs (e.g., the maximum happiness of all sentient beings, or maximum achievements of culture). Many people think of morality differently: as grounded in relations between persons and the specific duties we owe to one another. That morality is fundamentally about moral relations between persons, and not about the relations of persons to states of affairs, is the intuitive idea behind Kantianism and contractualism. Parfit incorporates Kant and contractualism as two parts of his Triple Theory. But then he insists, with little argument beyond his intuitive responses to Trolley-like examples, that the very rules that are justifiable to all, and to which all could rationally consent, are the selfsame rules that maximize good states of affairs.

How does he arrive at this conclusion? Surely it cannot be an inductive inference drawn from a few Trolley examples. Instead he says, “If we are asked how we can recognize such truths, we should appeal, as Sidgwick claims, to our intuitions.” Like many other non-consequentialists, however, I do not share Parfit’s abstract intuitions. Take the “Axiom of Personal Impartiality,” that everyone’s good is equally important. Even assuming that “no one could ever deserve to suffer,” surely we should not be equally concerned with promoting the happiness and well-being of sadists and other evil people (e.g., Hitler, Stalin). Also I do not have a “normatively indubitable” belief that morality and justice are expedient ways to optimize good states of affairs. It would clarify matters if Parfit were more specific about the good that is to be optimized. Sidgwick said universal happiness is the sole “ultimate good” to be promoted by all conduct.

Parfit similarly thinks that happiness is intrinsically good and that all suffering is bad. Unlike Sidgwick, however, he thinks that the distribution of happiness among people is important, especially compensation for suffering. He further says, noncommittedly and without discussion, that “friendship, love, knowledge, and various achievements may in themselves be good.” He is ambivalent about whether autonomy, or the freedom to choose and to determine one’s own life, is intrinsically good. What exactly is the good state of affairs that should be optimized by our conduct? Parfit does not answer this crucial question.


Even if these and other aspects of his account are inadequately defended, Parfit nonetheless provides the most serious attempt by a consequentialist to come to grips with Kant and bring him under the consequentialist umbrella. Parfit carries Sidgwick’s great project—the assimilation of the major contemporary moral philosophies to some version of consequentialism—much further than Sidgwick or anyone else. Parfit’s other major contribution is his defense of the objectivity of value. Here you don’t have to be a consequentialist to agree with Parfit; indeed many who are nonconsequentialists would make such a defense. Parfit challenges the pervasive subjectivism and relativism that prevails in academic culture and beyond. This is not just a philosopher’s issue. Every philosophy professor is confronted with students’ facile moral relativism. That Parfit fiercely challenges such views is one of the more admirable things about his book. He calls into question our culture’s peculiarly ambivalent position toward its own values.