Good people make us feel uncomfortable; they remind us that practising consistent generosity and selflessness isn’t nearly as impossible as we like to think. And so it is not at all surprising that we try our best to find ways of softening the embarrassment, looking eagerly for hypocrisy, inconsistency, mixed motivation or reductive explanations. Larissa MacFarquhar’s excellent book is, among other things, a bracingly sceptical examination of our scepticism. As well as giving us a series of vivid portraits of spectacularly altruistic individuals (and families), she offers a sketchy but highly intelligent overview of the various ways in which we set out to diminish those we like to call ‘do-gooders’, and concludes that these evasions won’t do: the hard question remains. If selfless devotion to relieving the pain or need of others is possible, why don’t more of us get on with it?

The book’s title relates this to the conundrum in moral philosophy that focuses on the limits of ‘disinterested’ care for others. Given the choice between rescuing a drowning relative or a total stranger in a situation of disaster, which do we go for? Does a thirty-year-old mother of four have more claim on me than my own ageing parent or unmarried sibling? It seems at first sight that a truly disinterested, truly generous love would make no fundamental differentiation between those who happen to be close to us and anyone else, so any decision about which one to give priority to would have to be made on grounds that had nothing to do with accidents of connection or instinct. MacFarquhar, by setting her narratives of ‘moral extremity’ in the context of this dilemma, highlights the way in which her heroes and heroines of moral consistency have to find some kind of calculus by which to make decisions about their ethical priorities. And this, of course, is where the problems begin.

Thornton Wilder’s once-celebrated novel The Bridge of San Luis Rey depicts a conscientious missionary friar attempting to find an explanation for a dramatic accident with multiple fatalities by allocating to each of the victims a carefully calculated score for virtue, piety and usefulness (the explanation being that an act of God would quite properly dispense with low scorers). But the novel makes it clear that he has missed the point in each case: it may well be, the narrative suggests, that each victim has indeed come to a point where death makes a kind of sense – but not for any reason that the hapless friar could possibly work out. Scoring systems in regard to human worth are fallible at best, and at worst an excuse for ignoring certain categories of person. Never mind ageing mothers; faced with two drowning strangers, one the proverbial mother of four, the other a young adult with Down’s syndrome or a hardened alcoholic, should the same disinterested reasoning apply as with our relatives? But unless we are to ignore certain kinds of human suffering or certain kinds of human being, the less apparently ‘useful’ do have actual needs that deserve to be met; if everyone applied the same calculus, who would ever ‘rationally’ make these people their priority?

MacFarquhar frequently discusses the ideas of Peter Singer, the Australian ethicist whose passionate insistence on a fully rational morality based on detailed calculations of the effectiveness of specific acts and policies has had a huge influence on popular movements such as the Oxford-based Giving What We Can network. Many of the people we meet in the book have been deeply marked by Singer and his followers, who offer a lucid and practical programme for maximising the effectiveness of charitable generosity through painstaking research and unsentimental assessment of results. There is a lot to be said for this as a basis for action. But two uncertainties remain, one fairly specific, the other larger and more elusive. Singer and others are clear that the most effective way you might help in – say – relieving global poverty or disease may not be to work as a grassroots development economist or a medical volunteer in South Sudan, but to take a highly paid job in your own country and donate a correspondingly large sum. There is much common sense in this and it usefully deflates the dramatic impulse that tempts us to think that we help best when we suffer most, even if this means we are largely ineffectual. But it leaves hanging the question of how there might ever be a world in which the coexistence of vastly (irrationally) paid jobs in the developed world – in the financial services sector, for example – and lethally fragile economies elsewhere is not just taken for granted. The model still seems to be bound up with the practice of the rich showing benevolence towards the poor, rather than any longer-term structural adjustment in the direction of greater equality or mutuality.

This connects with the broader point. There is often an assumption in all this that ‘goodness’ is about finding and enacting the most uncomplicatedly virtuous course of action, and that such a course of action is defined quite strictly in terms of the quantifiable relief of suffering. Once again, this is a helpful corrective to vagueness and self-serving fantasy. But what if ‘goodness’ also had something to do with a quality of relation with those who receive help, not just with the long-distance solving of their problems for them? What if morality had more to do with habit and character, with the grace of receiving as well as of giving, rather than being just the sum total of right actions? Singer and many (but not all) of the figures whose stories feature in Strangers Drowning are committed Kantians in their ethics: they believe that morality is about the quest for the unequivocally good action. But, as the dilemmas flagged in the title should tell us, there are choices in which there is no unequivocally good outcome. Talking as though there were one can imperceptibly encourage us to ignore certain kinds of suffering or pain in the way touched on earlier. As many moral philosophers have insisted over the last few decades, focusing on how to make infallibly right choices (and also on hard cases where this looks practically impossible) isn’t a very useful way of thinking about a good life as opposed to an ensemble of right answers. Part of the discomfort generated by some of MacFarquhar’s case studies is to do with a sense that some people are looking almost obsessively for a scheme of ideas that will assure them beyond doubt that they are doing what is right. The more sympathetic figures in this book are those who ruefully acknowledge that their moral maximalism cannot ever quite deliver this and that the human cost along the way may be disturbingly high; or those whose generosity has about it some dimension of warmth or joy as well as effectiveness.

The rest of the discomfort, of course, is exactly what we began with: the knowledge, for most of us, that we are simply not doing what we can. MacFarquhar concludes with a brisk and clear-eyed defence of her heroes. Granted, the world would be unrecognisably bizarre if everyone acted on the principles that inspire these men and women, but it would equally be unrecognisably static and self-satisfied and unjust if no one did. The strength of this insightful and grown-up book is to leave the discomfort in place without succumbing to a new sentimentality or absolutism.