I shall explore the prospects for a minimalist theory of normative ethics. By “minimalist” I mean a theory (analogous to minimalism in linguistics) that seeks to base normative ethics on the most exiguous of foundations, viz. a single moral principle, with other aspects of the ethical life consigned to something extraneous to morality strictly conceived. The moral principle in question is exceedingly familiar: DO NO HARM. That is all that morality contains, according to the minimalism I envisage, neither more nor less. The only moral principle is the injunction not to do harm. Usually this principle is included in a total utilitarian package: Do no harm and maximize wellbeing (welfare, the good, happiness, pleasure). I propose to drop the second conjunct so that morality only prescribes the avoidance of harm. Clearly the two conjuncts are logically independent, though the second is generally taken to include the first: if our aim is to maximize wellbeing, it should surely include minimizing harm. But we may live in a possible world in which there is no harm to be undone or produced, yet still we are subject to an injunction to maximize wellbeing—we must increase the level of wellbeing even if there is no suffering to be eliminated and none that can be produced (this is a world of harm-proof people). More obviously, one could accept the injunction not to harm while rejecting the injunction to promote wellbeing: I mustn’t harm anyone, but I have no duty positively to improve anyone’s lot. For example, I must not strike an innocent man for no reason, but I am under no obligation to make him happier than he already is. So I propose dropping the second injunction while insisting on the first. I call this position “disutilitarianism” because it emphasizes the avoidance of disutility not the production of utility. It is a negative prohibition: it says what we must not do not what we must do. We must not cause harm, though we have no duty to cause its opposite (if it has a real opposite)—we have no duty to maximize the general good, or even to produce it in a particular case. There is a duty against maleficence, but no duty of beneficence.
Let me immediately address a natural objection, namely that it is clearly morally praiseworthy to promote the good. I don’t disagree, though there are notorious cases in which promoting the good is not the morally right thing to do (the bane of utilitarianism); but I would distinguish between what morality requires and what it is admirable to do. It certainly shows the virtue of generosity to help the poor and needy, but that is not the same as saying that this is a moral duty. It may just be supererogatory. We have a duty not to harm, but we have no comparable duty to make people happier—though it might be virtuous so to do. I will come back this point, noting now only that moral minimalism does not preclude acting virtuously in promoting wellbeing; it claims only that this is not part of morality in the strict sense. We might even say that not causing harm isn’t a virtue at all, being merely our most basic moral obligation—there is nothing virtuous in declining to strike an innocent man for no reason. Duty and virtue are separate domains.
A main reason for advocating moral minimalism as against full-blown utilitarianism is that the stronger doctrine runs into well-known problems. I won’t rehearse these problems, but they concern considerations of justice and the problem of moral inflation, whereby we turn out to be the moral equivalent of murderers by not helping starving people in distant lands to the point of self-impoverishment. What is crucial, I think, is that there is a deep asymmetry between harming and benefitting: we have an absolute duty not to do the former, but the latter is optional. Partly this is because of the difference between pain and suffering, on the one hand, and happiness and wellbeing, on the other: the former are clearly defined and obviously bad, while the latter are amorphous and not invariably good (e.g. the pleasure-loving happy sadist). The dentist must do his best to avoid hurting you, but he is under no obligation to make you feel happier when you leave his office than you were when you came in—and what exactly would that be? He knows how to avoid harming you, but he may have no idea what would make you happier (a joke, a donation, a pat on the back?). So the harm principle has a different deontic status from the benefit principle. This is of course exactly how we operate in daily life: you avoid stepping on people’s toes as you walk down the street, but you don’t try to cheer everyone up as you pass them by. They will blame you for hurting them, but not for failing to improve their mood. They may think that that is none of your concern, while avoiding crushing their toes indubitably is. So we can say that the harm principle has a greater hold on us than the benefit principle; I propose accordingly that we restrict morality to the harm principle. 
It is a significant fact that all the standard rules favored by the deontologist can be seen to stem from the rule against causing harm. Breaking promises, lying, stealing, assaulting, murdering, acting unjustly—all involve causing harm to others. These rules are prohibitions designed to minimize suffering, ranging from disappointment to physical agony. None of them reflects the utilitarian’s insistence that we should maximize wellbeing—as if by sitting at home doing nothing we have committed grave evils. Of course, it is possible to harm by omission—and that is equally proscribed by the harm principle. You can fail to save someone from being hit by a car, so that your omission harms him or her. But doing nothing to make people happier is not ipso facto a form of indirect harm. We can’t somehow squeeze beneficence in under non-maleficence. The usual rules of morality concern things we are not to do (“Thou shall’t not…) and they all concern the harms that result from doing these things. Bringing each of these specific rules under the harm principle effects a major simplification, making moral thinking easier to manage and sharper in focus. All we really need to remember—all we need to know—is that it is wrong to cause harm. Whenever you are faced by a difficult moral choice you need only ask yourself what action will cause the least harm and then do that. For instance, you should not break a promise to meet A because meeting B instead will increase the total level of happiness in the world; you should avoid harming A by leaving him hanging (maybe suggesting to B that she finds something else to do). It is no small advantage to morality that it should be codified in a single easily remembered slogan. Children need to be instructed in it, and many adults have no aptitude for moral complexity, so keep it simple.
Can you harm someone in order to benefit him later? If so, there is no absolute ban on causing harm. Here we need to distinguish two cases: causing harm now to prevent greater harm later, and causing harm now in order to increase happiness later. The dentist drills the tooth now in order to prevent the pain of later toothache, so she is minimizing pain in the long run: that is morally acceptable and in accordance with the harm principle. But it is another thing entirely to try to justify causing harm now by citing future benefits that don’t involve harm minimization—as it might be, applying the rod to the child in the expectation that she will grow to be happier than she would be otherwise. This is far from obviously acceptable and it gains no support from the harm principle, which speaks only of minimizing harm not maximizing happiness. Omitting to do something harmful today can cause greater harm tomorrow, and is therefore morally proscribed; but omitting to do something harmful today that will result in less overall happiness in the future is not to be morally condemned (except by the rigid utilitarian). Even if beating children is known to make them happier in later life, that is no ground for beating them—though if it will prevent them from excruciating suffering later, then it should be done (however reluctantly). We must always seek to minimize harm, even if harm is necessary to bring that about; but harm can’t be justified by considerations of overall utility, as if pain now is made up for by elation later (as opposed to mere contentment).
It is important to minimalism to distinguish between what it is good for a person to do from what it is morally obligatory for a person to do. Minimalism is only a theory of the latter; it is neutral on the broader question of virtuous or admirable conduct. Living a good life includes acting generously and kindly, even if no harm is reduced thereby. That may seem to leave a lot of moral life outside the scope of the minimalist theory, but in fact it covers more than might be supposed. For much generosity and kindness involve the avoidance of suffering not merely the production of utility. You can harm someone by not being concerned about his or her welfare, as when you callously decline to give food to a starving person. But not all generosity is like that, as with the generous host: she is not avoiding harming her guests by laying on a great feast, but rather adding to her guests’ enjoyment. That is what is not morally required—increasing other people’s happiness. By not voting for tax increases to help the poor you may be harming them indirectly and by omission, so this falls under moral criticism; what does not invite moral criticism is declining to share your resources with people already amply resourced. So quite a lot falls under the prohibition against causing harm, not merely refraining from attacking people directly (animals too). Someone might be exceptionally generous with his friends, by always treating them to fancy dinners and the like; that may be commendable, but it is not morally obligatory. This is a distinction well worth preserving, and it is a virtue of minimalism that it makes the distinction firmly (unlike classical utilitarianism). Much virtuous behavior is discretionary, but moral behavior never is—it is strictly obligatory. Being a miser may not be admirable, but it is in a different category from being a sadist. The paradigm of the immoral act is maiming someone, not providing a thrifty meal instead of a lavish one.
Is the anti-harm theory deontological or consequentialist? You can take it either way, either as a moral rule or as a statement about consequences. That is, you can say that an action is right if and only if it actually minimizes harm, or you can say that the agent must always intend to minimize harm and that this is what makes it right not the actual consequences. I prefer to think of it as an absolute general rule with a number of sub-rules as special cases (such as “Don’t break promises”), but clearly the consequences are crucial in justifying the rule—pain and suffering being bad things in themselves.
I would emphasize the formal merits of the minimalist theory. It is simple, clear, manageable, and practicable. It is intuitively compelling and scarcely controversial in its recommendations (unlike utilitarianism). Its only questionable claim is that there is nothing more to morality than what it includes; but this is mitigated by the distinction between morality proper and what counts as virtuous conduct. It combines the best of deontology and consequentialism. It is what you would expect of a moral system that is designed to help people live together in close proximity. It is non-paternalist. It doesn’t seek to meddle in other people’s lives, as the prescription to make everyone as happy as possible does. It has a pleasing homogeneity. It is readily universalized. It does not attempt to combine disparate ideas (as in W.D. Ross’s mixed theory). It is easily teachable. It does not call for extremes of altruism and intolerable guilt over never doing enough. It takes what is good in utilitarianism and discards what is bad. The disutilitarian is a realistic, clear-eyed, compassionate, commonsense type of fellow, mainly concerned to prevent pain and suffering. Everything else is icing on the cake. If he can prevent us from harming each other (animals included), he thinks he has done his moral duty. What we choose positively to do, as a matter of personal virtue, is our own affair and of no concern to morality as such. 
 A further asymmetry is this: the harm principle applies impartially to intimates and strangers, but the benefit principle applies differentially according to personal distance (at least according to common morality). You must not harm anyone equally, but it is morally permissible to benefit members of your own family over others. This suggests that the harm principle is part of non-negotiable moral law, while the benefit principle operates according to personal discretion.
 The disutilitarian might well contend (echoing Nietzsche) that morality since the advent of Christianity has indulged in a kind of duty-creep whereby virtuous behavior has been converted into a species of strict moral duty. Thus Jesus urges us to give to the poor and needy (defined relatively) and his followers have interpreted this as an extension of our moral duties. But that is not necessarily the right way to interpret the words of Jesus: he is not assimilating charity to the deontic level of non-violence, merely suggesting that we cultivate the virtue of generosity and not content ourselves with the mere observance of our strict moral duty. Perhaps under the influence of Christian ethics, as it came to develop, utilitarian ethics made a virtue of blurring the line between moral duty and personal virtue, thus assimilating the demerit of not being charitable with the demerit of violently assaulting people. That was a conceptual error and one the minimalist is anxious to remedy.