Readers probably have a driving licence and so probably have been given the choice to become an organ donor. Some have agreed. In so doing, these readers have allowed that, if they die under suitable circumstances, their organs may be transplanted for the benefit of those in need. Other readers have refused. They are unwilling to become organ donors. They may explain that this is a private choice. They may prefer not to dwell on morbid possibilities. No matter, their choice – almost without exception – marks a gratuitous moral failure.

A familiar thought experiment, call it Pond, asks you to imagine walking past a shallow pond in which a small child is drowning. You can safely save the child's life but only at some expense to yourself: your shoes will be ruined. There is widespread agreement that in this situation you ought to save the child. Call this judgement Verdict. Notice, Verdict is tense-insensitive. We think if, in the future, one is confronted with a drowning child, one should save the child. And we think if, in the past, one was confronted with a drowning child, one should have then saved the child. So too is there a subjunctive variation of Verdict. One should be willing, were the occasion to arise, to save a drowning child.

One need not subscribe to any moral theory to see why one should accept Verdict. The cost to you is simply so low, and the benefit secured is so high, that on any plausible view you should perform the rescue. The case is an easy one. If one instead were to stroll past the pond as the child slipped below the surface, one would fail morally. And because the reasons supporting this act are vanishingly weak, the failure would be gratuitous.

Pond features prominently in debates about humanitarian aid. Peter Singer first offered it as part of an argument to the conclusion that we owe considerably more to the distant needy than is commonly thought. But many resist the extension of our intuitive judgements in Pond to the context of humanitarian aid. In accepting Verdict one accepts that on one especially favourable occasion one ought to incur a minor cost to confer a major benefit. Singer, by contrast, calls for radical and permanent changes to how we use our resources. Pond, moreover, involves a fairly straightforward course of action, with fairly clear consequences. Your shoes are ruined; a child is saved. It is less clear how your charitable contribution will be used. Finally, some regard as morally relevant the fact that the drowning child is a member of one's community. The distant needy are not. Thus, one may affirm Verdict, but deny that it delivers Singer's conclusion.

So Verdict doesn't settle debates about humanitarian aid. But it is relevant to another grave matter: the shortage of transplantable organs. For the considerations that tell in favour of Verdict also tell in favour of organ donation.

Consider another thought experiment. Walking past a hospital you suffer a brain aneurysm and die. Most of your organs remain functional and a team of surgeons is standing by to put them to use. It's too late for you, but if you've agreed to donate, your anatomical gifts will save many lives. If you haven't, the surgeons will do nothing and their patients will die. Reaching into your wallet they discover your choice.

We can now ask, in the subjunctive mood, whether you should have been an organ donor. I submit the answer is clear. Those who accept Verdict have even stronger reason to agree, in death, to donate their organs. Call this judgement Donate. One need not subscribe to any moral theory to see the appeal of Donate. Its requirements are straightforward. On one occasion you check a box, and if the circumstances of your death allow for it, your organs will be given to those in need. The cost to you is simply so low, and the potential benefit so high, that on any plausible moral view the present case is an easy one. Were you to prefer that your organs decompose with the rest of your body you would fail morally. And because the reasons supporting this act are vanishingly weak, the failure is gratuitous.

In many countries less than half of the population have agreed to donate. Are we to conclude, as I have suggested, that the rest have failed morally, and gratuitously so? Yes. This is a sad implication. But it is unavoidable. Consider some of the explanations offered by those who decline. And notice how very inadequate they are.

Clearly, to explain one's refusal as a matter of private choice is unacceptable. One must justify one's choice, not describe the conditions under which it's made. Perhaps whether one should act to save the drowning child in Pond is also a matter of private choice. And if one privately chooses to stroll past the pond knowing the child's lungs will soon fill with water, one has made a serious moral error. To call the choice private does nothing to justify it. So too with the choice not to donate. Private or not, it's a moral mistake.

Equally unconvincing is appeal to the discomfort of the choice. The prospect of one's death is unpleasant. But is it so distressing that one shouldn't be expected to reflect for a moment on the choice to be an organ donor? No. You are asked on one occasion to consider donation. Once the question is posed, awareness of your mortality is inescapable. Perhaps it will be suggested that declining to donate is less distressing than agreeing. And perhaps that's true. What, then, should we think of the comparison between the cost of choosing, and the benefits of having chosen? To judge that a moment of distress should change the balance of reasons is to grossly overestimate the moral importance of your own serenity. Return to Pond. Suppose if you perform the rescue you'll be shaken by the precariousness of life. Or you can stroll past serenely, undisturbed. That you must still perform the rescue, despite the distress, is obvious.

Here is another unfortunate bit of reasoning. Some elect not to become organ donors because they worry that the recipient of their gift may be undeserving. Perhaps their liver will go to an alcoholic or their lungs to a smoker. This is uncompelling. It is not at all obvious, and it is probably false, that one who is responsible for their poor health is undeserving of life-saving assistance. But even if this were so, it would provide no challenge to Donate. For, the recipients of one's gifts may not be undeserving. Return to Pond. Suppose it is unknown whether it is an innocent child drowning, or a reckless alcoholic. No matter, one should still perform the rescue. For it remains true that an innocent life might be saved. Anyway, even if we stipulate that the recipient is undeserving, one's donation would shorten the waiting list, thereby improving everyone's odds of getting a transplant.

Consider a final explanation. Some distrust medicine and choose not to become donors out of fear that they'll later receive less enthusiastic medical care. They worry their deaths will be hastened so that their organs may be made available. This explanation differs from the others in that, if true, it would supply some reason to resist Donate. But there's no reason to believe that it's true. It's imaginative speculation. It falsely assumes that those administering care know and make choices on the basis of one's status as an organ donor. It also implies that medical professionals are an unscrupulous bunch. Here's another unfounded bit of speculation: if you're not an organ donor the unscrupulous bunch will deem you selfish and so less deserving of enthusiastic care. Here's some more: donor or not, the unscrupulous bunch will take your organs if they please. No evidence supports any of these possibilities. Each is incredible and none should influence one's choice to become an organ donor. Return to Pond. This conditional is true: if the water is teeming with bloodthirsty sharks you shouldn't attempt the rescue. But this only supplies reason to reject Verdict if there is reason to believe that the antecedent is true. There is no such reason. Nor is there reason to think that if you're a donor your death will thereby be hastened.

Can we imagine a person who is neither an organ donor nor a gratuitous moral failure? Yes. Perhaps this person has never been asked about donation, and has never realized the option was open. Perhaps this person labours under false beliefs that were non-culpably acquired. Perhaps also they are non-culpably unable to apprise themselves of the facts. Such a person may exist. But this does not describe my reader.