Based on a speech given by Sebastian Wang to his school debating society

Weapons differ not merely in their destructive capacity but in the moral structure of their use. Some weapons are directed toward identifiable combatants and operate within spatial and temporal limits. Others, such as biological weapons, possess a radically different character: they are inherently expansive and largely indifferent to the moral distinctions that govern just conduct in war. A pathogen, once released, does not remain confined to the intentions of its creators. It spreads according to biological laws, not moral ones, and thus threatens to dissolve the distinction between combatant and non-combatant that lies at the heart of Christian moral reasoning about war.

Recent debates surrounding gain-of-function research, laboratory safety, and pandemic preparedness have brought renewed attention to these issues. Critics argue that certain forms of research, justified under the language of preparedness, may in fact introduce risks of catastrophic scale. Whether or not every empirical claim in such critiques is ultimately substantiated, the underlying moral question remains pressing: can the deliberate creation, enhancement, or deployment of disease ever be reconciled with Catholic teaching?

From the standpoint of the Catholic moral tradition, the answer must be negative. This conclusion does not depend on disputed empirical claims but follows from fundamental principles articulated by St Augustine, St Thomas Aquinas, and the broader tradition of Christian ethics.

The Sanctity of Human Life

Catholic moral theology begins with the affirmation that every human being is created in the image of God:

“God created man in his own image.”
— Genesis 1:27

This doctrine grounds the intrinsic dignity of the human person and establishes a moral limit on all forms of political and scientific action. Human beings are never merely instruments to be used for strategic advantage. As Aquinas argues, the good of the human person is not reducible to the good of the political community; rather, political authority exists to serve the flourishing of persons ordered ultimately to God (Summa Theologiae, I–II, q. 90, a. 2).

Biological weapons are uniquely incompatible with this principle because they operate in a manner that is intrinsically indiscriminate. Unlike conventional weapons, which can at least in principle be directed toward specific targets, pathogens spread through populations without regard for moral status. An engineered virus released against an enemy force may infect civilians, neutral parties, and even the population of the state that deployed it.

This indiscriminate character is not merely an accidental feature but a defining property of biological agents. As such, their use directly contradicts the requirement, articulated in the Catechism, that the use of force must not produce evils greater than those it seeks to remedy (CCC 2309). A weapon whose effects cannot be contained within morally permissible boundaries cannot satisfy this condition.

Just War and Moral Limits

The Just War tradition, developed by St Augustine and systematised by St Thomas Aquinas, provides the framework within which the morality of warfare is assessed. Augustine insists that war, even when justified, must be ordered toward peace and governed by charity. In The City of God, he writes that just wars are those that avenge wrongs and restore order, but he also emphasises that the inward disposition of the agent—particularly the avoidance of cruelty and hatred—is essential.

Aquinas formalises this tradition by identifying three necessary conditions for a just war: legitimate authority, just cause, and right intention (Summa Theologiae, II–II, q. 40, a. 1). Later developments in Catholic teaching add further criteria, including proportionality and discrimination between combatants and non-combatants.

Biological warfare fails most clearly at the level of discrimination. Aquinas does not explicitly address modern weapons, but his broader moral framework implies that actions which directly or foreseeably harm the innocent in an indiscriminate manner cannot be justified. The principle of double effect, often invoked in discussions of collateral damage, requires that harm to non-combatants be unintended and proportionate. In the case of biological weapons, however, the spread of harm to non-combatants is not merely a side effect but an inherent feature of the weapon itself.

Moreover, proportionality becomes impossible to assess when the effects of a weapon are unpredictable and potentially global. A pathogen does not cease to act when a military objective has been achieved; it continues to propagate according to biological dynamics that may far exceed the original intention. In this sense, biological warfare represents a breakdown of the moral control that Just War theory presupposes.

The Limits of Scientific Dominion

The ethical concerns surrounding biological warfare extend beyond its use to its development. Contemporary debates about gain-of-function research raise questions about whether certain forms of scientific inquiry involve deliberately increasing the transmissibility or virulence of pathogens in order to anticipate future threats. Even when pursued with defensive intentions, such research introduces risks that must be evaluated within a moral framework.

Catholic teaching affirms the legitimacy of scientific inquiry as a form of participation in God’s creative order. Aquinas holds that human reason is capable of understanding and ordering the natural world, and this capacity is itself a reflection of the divine intellect. However, this participation is not unlimited. Human dominion over creation, as described in Genesis, is a form of stewardship rather than absolute control.

The temptation to exceed these limits is rooted in the human condition. Augustine interprets the Fall as a disordered desire for autonomy—a turning away from God toward self-sufficiency. The aspiration to “be as gods” (Genesis 3:5) manifests in various forms, including the attempt to exercise total control over life and death.

In the context of biological research, this temptation may appear as the desire to master disease by recreating or enhancing it. While the intention may be defensive, the act itself risks crossing a moral boundary by introducing into the world entities whose potential for harm exceeds our capacity to control them. Aquinas warns that human action must be guided by prudence, which involves not only knowledge of means but also right judgment about ends and risks (Summa Theologiae, II–II, q. 47). Research that creates disproportionate risks to human life cannot be justified by speculative benefits.

Secrecy and Moral Responsibility

The development of biological weapons has historically been accompanied by secrecy, often justified on grounds of national security. While some degree of confidentiality may be necessary in military affairs, secrecy cannot absolve individuals or institutions of moral responsibility.

Augustine emphasises that all human authority is subordinate to divine judgment. No political or scientific institution operates outside the moral order established by God. The prophetic tradition reinforces this point by condemning those who attempt to conceal their actions from divine scrutiny:

“Woe unto them that seek deep to hide their counsel from the Lord.”
— Isaiah 29:15

Aquinas similarly insists that obedience to authority is not absolute. When commands conflict with the moral law, individuals are bound to follow conscience rather than authority (Summa Theologiae, II–II, q. 104, a. 5). This principle applies equally to scientists and policymakers. The claim that one is “only conducting research” does not eliminate personal responsibility for foreseeable consequences.

International Responsibility and the Common Good

Biological weapons pose a unique challenge to the concept of the common good because their effects are not confined to national boundaries. A pathogen released in one region may spread globally, affecting populations that have no connection to the original conflict. This characteristic undermines the very notion of war as a conflict between defined political communities.

The Catechism teaches that political authority exists to promote the common good, which includes the protection of life and the conditions necessary for human flourishing. Actions that introduce global risks of catastrophic harm are incompatible with this mandate. Aquinas defines the common good as a good that is shared and communicable; it cannot be achieved through means that threaten the basic conditions of human existence.

Furthermore, the pursuit of security through the development of biological weapons reflects a form of moral short-sightedness. Augustine warns that earthly peace, when pursued without reference to divine order, can become disordered and self-defeating. Efforts to secure one nation by endangering humanity as a whole ultimately undermine the very stability they seek to achieve.

Christian Stewardship and Ethical Science

A properly ordered approach to science must be grounded in the virtues of prudence, justice, and charity. This entails a commitment to research that serves the preservation and healing of human life rather than its manipulation or destruction. It also requires transparency, accountability, and international cooperation in regulating activities that pose global risks.

From a Thomistic perspective, knowledge is a good, but it is not the highest good. It must be ordered toward the ultimate end of human life, which is union with God. Scientific progress that disregards moral limits becomes disordered and potentially destructive. As Aquinas notes, the moral quality of an action depends not only on its object but also on its end and circumstances. Research that creates disproportionate risks to human life fails this test.

Conclusion

Biological warfare represents a profound challenge to the moral framework developed within the Catholic tradition. Its inherently indiscriminate nature, its resistance to moral control, and its potential for global harm place it in direct conflict with the principles articulated by Augustine and Aquinas. The Christian response must therefore be one of principled rejection. This rejection is not based on fear or technological pessimism but on a coherent moral vision that recognises the dignity of the human person and the limits of human authority. Christ’s ministry, centred on healing and restoration, provides the ultimate model for the use of knowledge and power.

A civilisation that seeks to weaponise disease risks undermining the very foundations of its moral order. If science is to remain a genuine good, it must be guided by wisdom and oriented toward the service of life. Only within such a framework can it fulfil its proper role as a participation in God’s creative and redemptive work.

Suggested Reading

Sacred Scripture

• Genesis 1–3
• Matthew 5–7
• Luke 10:25–37
• Romans 12
• James 3

Catholic Teaching

• Catechism of the Catholic Church, §§2258–2330; §§2302–2317
• St Augustine, The City of God, Book XIX
• St Thomas Aquinas, Summa Theologiae, II–II, Question 40 (“On War”)
• Pope St John XXIII, Pacem in Terris (1963)
• Second Vatican Council, Gaudium et Spes, §§79–82
• Pope St John Paul II, Evangelium Vitae (1995)

International Law and Ethics

• Biological Weapons Convention (1972)
• World Medical Association, Declaration of Geneva
• James Turner Johnson, Just War Tradition and the Restraint of War
• Paul Ramsey, The Just War

Scientific and Historical Background

• The Bioweapons Industry’s Most Dangerous Lie is an example of contemporary criticism of gain-of-function research and laboratory safety, to be read critically alongside primary scientific literature.