The thought experiment is simple enough to be taught to undergraduates and troubling enough to haunt adults. You are walking past a shallow pond when you see a child face-down in the water. You can wade in and pull him out, but doing so will ruin your shoes and muddy your clothes. Who but a monster would not agree that you should wade in and save the child, whatever the cost to your shoes?

The Australian philosopher Peter Singer held that the basic “intuition” most of us have about this situation expresses something deep and important about our shared ethical commitments. If it reflects something we really believe about the moral weight of preventable suffering, then it does not stay politely by the hypothetical water’s edge. It follows us home, into our budgets, our careers, our politics. The world is full of drowning children and we, the relatively affluent, are in a position to help them with a single bank transfer. Death in a Shallow Pond is David Edmonds’ account of how a single philosophical image escaped the seminar room and became an argument that now tugs, persistently, at the conscience of the affluent.

The thought experiment is simple enough to be taught to undergraduates and troubling enough to haunt adults. You are walking past a shallow pond when you see a child face-down in the water. You can wade in and pull him out, but doing so will ruin your shoes and muddy your clothes. Who but a monster would not agree that you should wade in and save the child, whatever the cost to your shoes?

The Australian philosopher Peter Singer held that the basic “intuition” most of us have about this situation expresses something deep and important about our shared ethical commitments. If it reflects something we really believe about the moral weight of preventable suffering, then it does not stay politely by the hypothetical water’s edge. It follows us home, into our budgets, our careers, our politics. The world is full of drowning children and we, the relatively affluent, are in a position to help them with a single bank transfer. Death in a Shallow Pond is David Edmonds’ account of how a single philosophical image escaped the seminar room and became an argument that now tugs, persistently, at the conscience of the affluent.

Edmonds admirably avoids both hagiography and invective. He is explicit that his book is “not a polemic.” Instead, he offers something closer to a genealogy: how the shallow pond thought experiment acquired its peculiar philosophical authority; how it traveled from the academic world of “applied ethics” into a fledgling moral movement; and why it has generated, alongside converts and donors, a distinctive recoil. The result is the rare book that treats a philosophical argument as a social phenomenon.

Singer emerges here not only as the name attached to a set of arguments but as a temperament, a person in whom calculation reliably dominates emotion, and as a man whose life and thought were shaped by exile and the aftershocks of war and genocide. The book is full of deft, disarming details: Singer’s activism moving from the Vietnam War and abortion reform to what would become his signature causes of animal suffering and global poverty. These biographical facts are not offered as crude explanation but as context for a moral seriousness unusually willing to offend common sense.

Singer was the beneficiary of a particular intellectual moment. Oxford in the late 1960s and early 1970s was a discipline in the middle of a quiet revolt. In a world marked by the Vietnam War and the Holocaust’s long shadow, the analyses of ethical language that had dominated the 1950s were beginning to feel distinctly evasive. The rise of applied ethics, cemented institutionally in the founding of the journal Philosophy & Public Affairs, was neither inevitable nor universally welcomed. Singer arrived just as inhibitions about “moralizing” were weakening. Had he come earlier, or later, Edmonds suggests, the shallow pond might have remained a clever classroom puzzle rather than the most influential moral analogy of the past half-century.

Having set up this context, Edmonds traces the shallow pond’s most consequential afterlife: its translation into an influential movement whose adherents call themselves “effective altruists.” The movement, whose chief founders Toby Ord and William MacAskill met as graduate students at Oxford, takes Singer’s provocation and asks how far it can be systematized, institutionally, philanthropically, and politically, and rendered even more radical—applying, for instance, not just to those who presently exist but people in the distant future.

Effective altruism, Edmonds repeatedly reminds us, is not itself a moral theory. While many effective altruists are motivated by utilitarian reasoning, the movement presents itself as open-minded about its philosophical foundations, united less by doctrine than by a practical question: Given limited resources, how can we do the most good? Edmonds’ account of how that question hardened into a distinctive ethos of evidence-based giving, cost-effectiveness, and suspicion of sentiment is one of the book’s great strengths. He also shows, without caricature, how that ethos generates resistance: empirical doubts about aid; moral unease about the dignity of aid recipients; political worries about technocracy and elite authority.

Edmonds pays sustained attention, as other writers on this subject rarely do, to psychology. The shallow pond argument does much of its work by provoking a peculiar mix of guilt, admiration, irritation, and resentment. Edmonds treats this pattern of responses as things to be explained rather than dismissed. Yet here the book also shows restraint. It is one thing to catalogue why people resist Singer’s conclusions; it is another to ask whether that resistance might itself reveal something important about morality’s place in a human life. Edmonds repeatedly flags this possibility while leaving it to the reader to decide what, and how large, that place is.

The shallow pond isolates a small cluster of instinctive judgment—about rescue, urgency, and responsibility—and renders them vivid. The harder question is whether it can serve as the organizing image for a life one recognizes as valuable, or for a political movement capable of commanding widespread loyalty. For that, the values it makes salient must coexist with others many people experience as no less fundamental: commitment to family and friends, attachment to projects that give shape to a life, and forms of partiality not experienced merely as moral weakness. Utilitarianism can acknowledge these things, but typically only “derivatively,” as dispositions it is useful for us to have because they tend, in the long run, to produce good consequences. That is not how they appear to us from, as it were, the inside.

This gap between theory and experience was diagnosed most sharply by Bernard Williams, a critical figure repeatedly invoked in this book, who argued that some of our “projects” are not just things we happen to care about, but part of what makes a life one’s own. Singer has been taken to be saying that every seemingly innocent choice—time spent with your children, a coffee and croissant for breakfast—is implicitly a decision not to save a drowning child. The argument invites a form of ethical self-surveillance that threatens to flatten the distinction between what we morally value and what we value, full stop. Edmonds presents this worry with sympathy but stops short of asking whether a morality that persistently generates this kind of friction might be revealing not human failure, but moral overreach.

Some recent philosophical arguments have suggested that this resistance may simply reflect our discomfort with morality’s true demands. As the philosopher Nikhil Venkatesh puts it, utilitarianism shares something important with socialism: Both urge us to reevaluate the worth of our attachments in light of our nature as social beings whose lives are sustained by the labor and restraint of others. If that argument is right, then the alienation people feel in response to Singer’s conclusions is not a refutation but a symptom.

Effective altruists sometimes describe ordinary lives—lives structured around career, relationships, and personal projects, with only limited altruistic sacrifice—as ethically suboptimal. That description may be correct by utilitarian lights. But it is an open question whether the reason many of us live such lives is merely weakness or blindness. Could it not be that those are the lives we think we have reason to live, all things considered?

Perhaps the hostility Singer’s arguments provoke is not best understood as confusion or weakness, but as resistance to any morality’s claim to sovereignty over a life. Nietzsche, a figure Edmonds doesn’t mention, invited us to consider the deeply unsettling thought that human indifference to most suffering was not just a forgivable compromise for the sake of our sanity, but in itself a very good thing responsible for much that is good in human life.

Notably, effective altruism itself has retreated from the most demanding implications of Singer’s original argument. Its leading figures now stress that constant optimization is self-defeating: A scientist who tried to make every daily decision maximally altruistic would likely abandon the very research that might, in the long run, save thousands of lives. This is why radically altruistic psychologies—the people who give away everything down to their surplus kidney—are typically treated with ambivalent admiration. Larissa MacFarquhar’s profiles of such maximal altruists, Strangers Drowning, a natural companion to Edmonds’ book, captures this fact with extraordinary sympathy.

In the end, there are two stubborn facts to be explained. The shallow pond elicits recognition: a sense that something important has been revealed. And it elicits resistance, irritation, defensiveness. Edmonds’ great achievement is to take both reactions seriously, and to let the philosophers and economists who articulate them speak at length.

Effective altruism in its various forms draws out one powerful strand of our values: responsiveness to suffering and preventable harm. What they have not shown, and may never show, is that our attachments, loyalties, and projects are illusions to be overcome rather than sources of meaning that also deserve our allegiance. Death in a Shallow Pond does not resolve that tension. But by tracing how one small moral image came to embody it so vividly, Edmonds has written the rare philosophical book that leaves the reader both clearer-headed and more honestly conflicted.