The answer to this question seems obvious. Legally, there is a significant difference between killing someone and letting them die. Killing somebody by active means, depending on the circumstances, might be treated as murder, manslaughter or causing death by dangerous driving for example, all of which are subject to serious punishments. On the other hand, letting somebody die might attract no penalty at all, because this is what we all have to do at some point when medical options are unavailable or not in a person’s best interests. In the case of Airedale NHS Trust v. Bland, the House of Lords judgement “thou shall not kill, but thou needst not strive officiously to keep alive.” When it is in a patient’s best interests it can be the right thing to do to do nothing and let them die. Even where a doctor is negligent and allows somebody to die who might have been saved the penalty is much, much less than if they actively killed somebody – and usually covered by insurance. Nevertheless, despite the obvious answer, the question concerns the moral and not the legal difference between killing and letting die. The answer to this is more contentious. On the one hand traditional Christian Ethics and Kantian Ethics would agree with the law, that there is the world of difference between killing and letting die, but on the other hand, Utilitarianism and Situation Ethics as consequentialist approaches to decision-making would reject that distinction, arguing that the effects of both are the same so as actions they are morally equivalent. Nevertheless, the claim that killing and letting die are morally equivalent is not persuasive. Consider other examples whereby the same effects are achieved by different means. Is there a moral difference between actively lying to a friend or not telling them something that you might have? Is there a moral difference between making somebody homeless and failing to help a homeless person by housing them? Most people would see acts of omission (failing to do good) as less morally serious than acts of commission (i.e. actively doing wrong), so there is a moral difference between killing and letting die.

Firstly, the fact that there is a difference between killing and letting die is supported by the Bible, which distinguishes between things we do intentionally and accidentally and things done actively and passively. In the Old Testament the penalty for murder (intentional, active killing of a person) was death [Genesis 9:6], but nobody suggested that fellow citizens should be executed for failing to feed famine victims. The moral instruction to leave crops for the poor to glean existed of course [Leviticus 23:22], but there was no specific and individual penalty for ignoring it. While Prophets warned that the people would be punished collectively for ignoring the rights of the poor and vulnerable [e.g. Amos 2], suggesting that ignoring these rights is immoral and against the will of God, there can be no doubt that there is a moral difference between active, intentional killing (murder) and letting die, whether intentionally or otherwise. On the other hand, in the New Testament Jesus equated the intention with the action in his moral teaching. In Matthew 5 He taught that anger was morally equivalent to murder, a lustful look morally equivalent with adultery. By this logic, allowing somebody to die with malign intent would be the equivalent of murder, and yet this principle has rarely, if ever, been adopted by Christian ethics. Perhaps the key to this issue is what the word “morally” means. Because it is often impossible to know what motivated an action it is not possible to put a lot of weight on intentions in law or in formal Christian ethics. A person might even be unsure about their own motivations, so it is extremely difficult to assess these objectively. Nevertheless, Christians believe that God knows the inmost secrets of our hearts, being aware of motivations that we might not even be aware of ourselves [Psalm 139]. In this case, intentions might make all the difference to the moral status of an action in God’s eyes, while in the eyes of formal Christian ethics they cannot. Having said that, a Roman Catholic might argue that the Church has been given the authority to “bind and loose” Matthew 18:18, and this would suggest that the moral judgement of the Church – which cannot give much weight to intentions – still applies in heaven. This suggests that there is a moral difference between killing and letting die, whatever the situation or motivations, although that does not mean that letting die is always morally permissable.

Secondly, most versions of Natural Law (used alongside the Bible and Church teaching as the basis for Roman Catholic Ethics) teach that actions are more significant than intentions, which suggests that there is a moral difference between killing and letting die. For example, because of Natural Law Catholic ethics would see it as far worse to use artificial contraception or abortion than to remain celibate and so childless. Contraception and abortion actively prohibit a basic human good – life – while celibacy might be necessary in order to achieve another human good, as in the case of Priests. Morally, there is a real difference between doing something – often for an evil intention – and committing not to do it for a good intention. In Summa 2i, 20, 1 Aquinas explains that an action may be good when carried out with a good intention, but morally evil when carried out with an evil intention. He uses the example of giving alms – good when done out of agape-love and evil when done for vainglory. This implies that saving a life might be good when in the best interests of a patient, but morally evil when done for other reasons, in which case allowing to die might be morally preferable. The same reasoning might suggest that killing would be morally wrong when done with a malign intention and potentially right when done with a loving intention, yet Aquinas stops short of this conclusion. He reasons that while it is a duty to follow synderesis, even if it leads us to make such a faulty decision, this does not excuse us if we carry out actions which contradict conscientia, as killing a person always would because it actively prohibits the basic human good of life. It follows that the wrongness of killing is not dependent on motivations, and yet the situation does make some difference. Aquinas acknowledged the difference between not acting in cases where you can and should act and not acting when you can’t do anything or shouldn’t because of an order etc. He wrote “the cause of what follows from want of action is not always the agent as not acting; but only then when the agent can and ought to act.” [Summa 2i, 6, 3] This suggests that letting a relative die when you can’t help or have been ordered, such as by a court, not to would be morally very different from letting a patient die as a doctor when you could and are allowed to help. Further, in Summa 2i, 76, 3 Aquinas notes that ignorance might reduce the sinfulness of an action, because it makes some actions involuntary, when “voluntariness is essential to sin.” In this way, there would be a moral difference between a person whose synderesis led them to kill an elderly relative out of compassion and a person who intentionally killed an elderly relative in order to benefit from a will. Nevertheless, this interpretation would be strongly rejected by the Roman Catholic Church today, which teaches that any active euthanasia is the moral equivalent of murder, evil. In 2020 the Congregation for the Doctrine of the Faith has reaffirmed Roman Catholic teaching that euthanasia is an “intrinsically evil act”. The letter Samaritanus Bonus: On the care of persons in the critical and terminal phases of life described assisted dying and euthanasia as “homicide”, and said that the sacraments must be withheld from those who are planning to end their lives. This underlines the moral difference that the Church perceives between killing somebody – regardless of motivations – and letting die.

Thirdly, Kantian Ethics agrees that there is a moral difference between killing and letting die. For Kant, the maxim behind our actions is the action considered independently of any context and, if it cannot be universalised, it is absolutely and always wrong. In this way killing a hated enemy, killing an elderly relative to benefit from their will, killing a relative who is begging for an easeful death and suicide are all morally equivalent. Because the maxim cannot be universalised, killing is absolutely wrong. Despite this, Kant also taught that intentions are even more significant in determining the moral status of an action than the action in itself. Famously, he began the “Groundwork for the Metaphysics of Morals” (1785) by stating that “Nothing in the world—or out of it!—can possibly be conceived that could be called ‘good’ without qualification except a GOOD WILL.” If an action is undertaken out of fear or habit or for any other reason than freely, for duty’s sake, then this renders the action morally wrong, which pollutes the will and prevents it being worthy of the eternal reward which we must postulate as existing for good wills, so that they can do as they feel that they should and so that the universe is fair. Further, Kant taught that a negative duty i.e. not to kill, lie or steal always trumps a positive duty e.g. to feed the hungry. This suggests that there is a moral difference between killing and letting die; while in some circumstances both are immoral, killing (achieving the end by active means) is always worse. Nevertheless, Peter Singer would reject this conclusion, arguing that there is little moral difference between killing and letting die. In “Practical Ethics” he argued that there is no moral difference between aborting a near-term foetus because it has a disability and killing a newborn infant. In fact, he argued that it is morally preferable, even a moral duty, to kill a newborn who is suffering and who has no hope of a quality life so that money spent on neonatal care could be spent more productively elsewhere. In “Unsanctifying Human Life” Singer and Kuhse argue the same with regard to Euthanasia, suggesting that it is morally preferable to kill an elderly relative with dementia than to allow them to die – slowly and expensively – while others suffer for lack of healthcare resources. Further, in “The Life you can Save” Singer argued that neglecting an opportunity to help somebody and killing them are morally equivalent. He used the example of a child drowning in a pond, pointing out that we would feel a moral imperative to ruin expensive shoes in order to save them… and that we should equally feel a moral imperative to save a child on the other side of the world by sending the £200 our shoes cost to a charity. Through all these cases, Singer makes a fair point in pointing out that we are wrong to place so much weight on the moral difference between killing and letting die. It is helpful to consider that letting die might well cause more suffering and that killing should not be the taboo that it is to most people, when in practical terms it may be preferable. Singer is also right to point out how most people wrongly prefer people who are close to us and choose to ignore those who are further from us, whether in space or time, meaning that we tend to be thoughtless and ignore the moral imperative to use our money wisely and avoid decisions which – however unintentionally – harm others now or in the future. Nevertheless, however right Singer is to make a theoretical point as regards the equivalence of killing and letting die, in practice it is not reasonable to treat the two as moral equivalents, because the law deals in rules and generalities, not intentions and specific situations. Further, as Onora O’Neill has argued, we can’t agree that failing to help somebody in need – such as by giving money for famine relief – is morally the same as killing them. While both are morally bad, killing is worse because it is active and intentionally evil.

Despite this, most consequentialists will agree with Singer, arguing that there is no moral difference between killing and letting die, because the consequences, which justify an action or condemn it, could be the same either way. Take for example a case of assisted dying; the patient is dying, so the only factor that decides the morality of killing them or letting them die is the amount of pleasure or pain that results from the action, so far as the patient and other interested parties are concerned. As Bentham pointed out “all other things being equal, poetry is as good as pushpin” or, in other words, what you do to produce the results is immaterial; all that matters, morally, is the results. This means that there is no essential moral difference between killing and letting die such as would make one better than the other in all situations. It may be that letting someone die produces more suffering than killing them would, as in a case of a patient dying of motor-neurone disease who has asked to “die with dignity” and whose relatives and friends are all supportive. In other cases however, killing would undoubtedly cause more suffering than allowing to die, such as when the law allows passive euthanasia but not active. In such a case, killing might get a doctor struck off and even imprisoned, even when their intentions were altruistic and good. The case of Dr Cox and Lilian Boyes shows how this could be the case. While the situation makes all the difference in terms of the moral status of the action, Utilitarians such as Jeremy Bentham would reject the idea that intentions make any moral difference; as he argues “nature has placed mankind under two sovereign masters; the pursuit of pleasure and avoidance of pain” so we should “always act so as to produce the greatest happiness for the greatest number…” what we intend is not at issue, only what we achieve in respect of pleasure and pain in society. This highlights one of the problems with consequentialism – what Peter Singer has identified as the biggest problem that Utilitarianism faces – the Problem of Prediction. That is, consequentialism depends on our ability to calculate the pleasure and/or pain resulting from possible actions so that we can choose the one which is morally preferable in maximising pleasure and minimising pain, in advance of doing anything. In practice, our calculations are often flawed meaning that while we intend to minimise suffering, in the end we fail to do this. Because intentions don’t count and the only thing that justifies an action, morally, is the consequences the agent takes a risk every time they act, trusting that what they intend will happen and so ensure that they have done what is right. In a case of euthanasia, for example, the situation is further complicated by the difficulty of assessing someone else’s pain, whether in the person dying or in their relatives and friends. How can we measure grief or accurately determine whether it is outweighed by the suffering a person dying, say of cancer, experiences in their final hours? Bentham’s felicific calculus, while well meant, is of little practical use when it comes to making such assessments and only serves to highlight another significant criticism of consequentialist ethics, that they are subjective. Of course, rule utilitarianism, such as that proposed by Peter Singer in recent years, gets round both the problem of prediction and the subjectivity problem by developing rules on the basis of the utilitarian maxim, which are then applied in most or all cases regardless of the details. Yet, as RM Hare pointed out, rule utilitarianism means that there is little difference between a Utilitarian and say a Kantian approach. Also, in answer to this question, it would probably mean that there is a moral difference between killing and letting die because rules tend to be framed around actions, not omissions and because it is hard to imagine a rule prohibiting letting people die being practical in many cases!

In conclusion, there is a moral difference between killing and letting die because this is the case in law, in the Bible, in Natural Law and Kantian Ethics. As has been discussed, it is also true in Rule Utilitarianism, which is really the only practical version of Utilitarianism.