The sanctity of life is the belief that human life is intrinsically valuable and sacred, often grounded in the idea that life is created in the image of God (imago Dei) and therefore possesses inherent dignity. This principle has been especially influential in religious ethical frameworks, most notably within Roman Catholic teaching, where it plays a central role in opposition to euthanasia, as well as in the Biblically based teachings of Protestant denominations. The principle of the Sanctity of Life has also influenced Kantian, Virtue and Human Rights frameworks. However, alternative approaches, particularly those grounded in utilitarianism and personhood theory, challenge the absolute status of the sanctity of life. Overall, while the sanctity of life remains an important consideration in decisions about euthanasia—especially in safeguarding against abuse and affirming human dignity—it should not be regarded as decisive, as it can lead to morally problematic outcomes when applied rigidly in cases involving suffering and autonomy.

Firstly, the sanctity of life is highly important within traditional religious approaches, particularly in the teaching of the Roman Catholic Church, where it provides a clear and consistent moral framework opposing euthanasia. The Church’s position is articulated in the Declaration on Euthanasia (1980), issued by the Congregation for the Doctrine of the Faith, which states that “nothing and no one can in any way permit the killing of an innocent human being.” This reflects the belief that life is a gift from God and that only God has authority over its beginning and end. Such a view is rooted in Natural Law, particularly the primary precept to preserve life, as developed by Thomas Aquinas. The strength of this approach lies in its consistency and its protection of vulnerable individuals; by rejecting euthanasia outright, it avoids the risk of coercion or the devaluation of lives deemed less “worthy.” Furthermore, it upholds a strong sense of human dignity that does not depend on physical or mental capacity. The fact that having the sanctity of human life can be the basis for a credible ethical approach is demonstrated by the work of John Finnis, who situated life as a basic human good that cannot be compromised in his “Natural Law and Natural Rights” (1980). However, critics argue that such an absolutist stance as is supported by the principle of the Sanctity of Human Life can lead to inhumane outcomes, particularly in cases of extreme suffering, where prolonging life may seem to conflict with compassion. Nevertheless, the sanctity of life remains a foundational principle within this tradition, demonstrating its significant importance in shaping ethical decisions about euthanasia.

Secondly, the sanctity of life plays an important role in secular ethical debates as a safeguard against the potential dangers of legalising euthanasia, even if it is not always treated as absolute. Upholding the intrinsic value of life can act as a barrier against the “slippery slope” argument, which suggests that permitting voluntary euthanasia could lead to non-voluntary or involuntary forms. By maintaining that all human life has value, societies can resist pressures to normalise ending life for reasons such as disability, old age, or economic burden. This concern is implicitly supported by religious frameworks but also resonates in broader human rights discourse. However, thinkers such as Peter Singer challenge the sanctity of life by distinguishing between “human life” and “personhood.” Singer argues that moral value should be based not on mere biological existence but on characteristics such as self-awareness, rationality, and the capacity to suffer. He controversially claims that “killing a person is normally worse than killing a non-person,” implying that some forms of euthanasia may be morally permissible or even desirable. While Singer’s approach allows for compassionate responses to suffering and prioritises quality of life, it also raises serious ethical concerns about who gets to decide which lives are valuable. In this context, the sanctity of life continues to function as an important counterbalance, ensuring that ethical decisions do not become purely utilitarian calculations.

However, the importance of the sanctity of life can be challenged on the grounds that it may conflict with other key ethical principles, particularly autonomy and compassion. Critics argue that an absolute commitment to preserving life can undermine an individual’s right to choose how and when they die, especially in cases of terminal illness or unbearable suffering. From a liberal perspective influenced by thinkers such as John Stuart Mill, respect for autonomy is central to moral decision-making, and denying a competent individual the right to end their life could be seen as an unjustified form of paternalism. This is reinforced by the work of Peter Singer, who argues that the capacity to suffer, rather than mere biological life, is morally decisive; where continued existence brings more suffering than benefit, euthanasia may be justified. Furthermore, even within the Roman Catholic Church there is recognition that preserving life is not an absolute duty in all circumstances. The Declaration on Euthanasia permits the refusal of “over-zealous treatment” and accepts that allowing death to occur may be morally permissible where burdens outweigh benefits. Similarly, the doctrine of double effect allows for actions such as administering high doses of analgesics that may hasten death, provided the intention is pain relief rather than killing. This suggests an implicit prioritisation of compassion and proportionality over the mere prolongation of life. However, this critique does not entirely undermine the importance of the sanctity of life. Rather, it demonstrates that even its strongest proponents recognise the need for nuance in its application. The principle continues to act as a moral constraint, ensuring that decisions about euthanasia are not reduced to purely subjective or utilitarian calculations. Therefore, although autonomy and compassion challenge its absoluteness, they do not eliminate its significance.  Nevertheless, it could be argued that the sanctity of life remains the most important principle in decisions about euthanasia because it provides a necessary safeguard against the dangers inherent in alternative approaches. Without it, ethical decision-making risks sliding into a form of utilitarianism that permits the devaluation of certain lives. Peter Singer’s distinction between “persons” and “non-persons,” for example, has been widely criticised for implying that individuals lacking rationality or self-awareness—such as infants or those with severe cognitive impairments—may have less moral worth. Critics such as Leon Kass argue that abandoning the sanctity of life leads to a “culture of death,” where human dignity is contingent and negotiable. In this context, the sanctity of life provides an essential moral foundation by affirming the equal and inherent value of all human beings, regardless of their capacities. However, this defence can be challenged. While the sanctity of life may protect against abuse, its rigid application can itself produce morally troubling outcomes, such as prolonging intense suffering against a patient’s wishes. Moreover, the slippery slope argument is often overstated; empirical evidence from countries where euthanasia is legal suggests that robust safeguards can be implemented. Therefore, while the sanctity of life is undeniably important as a protective principle, it should not be treated as overriding all other considerations. Its role is better understood as one element within a broader ethical framework, rather than the decisive factor.

In conclusion, the sanctity of life plays a significant but not decisive role in decisions about euthanasia. It provides a vital moral foundation, particularly within religious traditions such as the Roman Catholic Church, and serves as an important safeguard against the devaluation of human life. However, its absolutist application can lead to morally troubling consequences, especially when it conflicts with considerations of autonomy and the alleviation of suffering. The strongest argument against its ultimate importance lies in its inability to adequately address complex, real-world cases where preserving life may not align with compassion or individual dignity. Therefore, while the sanctity of life should remain a central consideration in ethical deliberations about euthanasia, it must be balanced with other principles to ensure that moral decision-making is both humane and context-sensitive.