Are Nuclear Weapons a Necessary Evil? Part 2: An Introduction to the Applied Ethics of Nuclear Warfare

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General Difficulty: A-Level, Undergraduate

Series Introduction

It is no exaggeration that August 6th 1945 saw one of the most horrific days in human history. At 8:15 in Hiroshima, Japan, a crew on the plane Enola Gay dropped the first-ever nuclear weapon, called ‘the Little Boy’. They watched as a whole city, thriving and bustling one second, disintegrated in the next. Tens of thousands of civilians ceased to exist with no trace of them left behind. As the crew looked down at the remains of the city, Captain Robert Lewis (the co-pilot) cried out,

‘My God, what have we done?’

What the crew witnessed was only the tip of the iceberg. Many more civilians suffered the agony of radiation poisoning, burns and cancer from the blast. Ecosystems were desolated. To this day, it is difficult to understand how the infliction of such cruel devastation could possibly be justified.

Despite the horror of the scene, those on the plane and American politicians defended the mission. Major Thomas Ferebee (the bombardier) believed that the deployment of the bombs saved many thousands of lives by ending the Second World War. Harry Truman, the US president at the time, said that the bombs were dropped to avoid killing citizens.

However, as time passed, opposition to nuclear weapons grew. Robert Oppenheimer, the scientist in charge of creating the first nuclear weapon, opposed the development of the hydrogen bomb (a far more powerful version of the bombs dropped on Japan) and spent the rest of his life advocating for proper controls on nuclear weapons. In 1955, Bertrand Russell (philosopher and political activist) and Albert Einstein (scientist) wrote the Russell-Einstein Manifesto to warn the world of the dangers of nuclear weapons. 

Despite the first nuclear weapon being dropped over 75 years ago, they have continued to terrorize the public. Today, with increasing global aggression, we are all on a knife edge of nuclear destruction. It is more important than ever to dive into the ethics of nuclear warfare.

This series aims to provide the reader with the foundations of the philosophy of nuclear warfare and look at questions such as whether it is ever ethical to use nuclear weapons or if nuclear deterrence is different to active use. It will look at normative approaches to nuclear weapons such as utilitarianism but also the unique challenges that nuclear weapons pose.

Post Introduction

The first post contextualized the nuclear weapons debate within its historical context. This second post will provide a background to the study of applied ethics and its application to nuclear warfare. It will explain what ethics and applied ethics are, the differences between top-down and bottom-up approaches, introduce the concepts of consequentialism and absolutism, the difference between active use of nuclear weapons and deterrence and how these combine to create three distinctive approaches to nuclear weapons.

Ethics and Applied Ethics

Questions about the use of nuclear weapons fall under the ethics branch of philosophy. This is the part that examines what makes an action good or bad. There are three key parts to this branch.

1.     Normative Ethics

Firstly, there is the normative ethics branch. This is where philosophers develop ethical systems, rules and theories that inform ethical conduct. An example of this is utilitarianism, which is the ethical system that argues an ethically good action is one that maximizes happiness. Other ethical systems include deontology and virtue ethics.

2.     Metaethics

The second branch is metaethics. This looks at what it means to say that an action is ‘good’. What does ‘good’ refer to? For example, emotivism holds that to describe helping an elderly person across the street as ethically good is to say that we have positive feelings toward the action.

3.     Applied Ethics

The final branch of ethics is applied or practical ethics. This is the ethical examination of particular cases or actions. For example, examining whether it is ethical to steal or do nothing while a person starves are examples of applied ethics.  The ethics of nuclear weapons falls under this category.

Top-Down, Bottom-Up and Reflexive Equilibrium 

Applied ethics often consists of two parts – ethical theory and action. There tend to be three approaches to this relationship – top-down (principlism), bottom-up (casuistry) and reflexive equilibrium. Each approach dictates the relationship between ethical theory and the specific instance being discussed.  

1.     Principlism

A top-down approach (or principlism) gives priority to the ethical theory with the action being secondary. An ethical theory is thus studied or created and then applied to a specific action. For example, a utilitarian may start with utilitarianism and believe it is the correct ethical theory. Utilitarianism is the theory that an action is morally good or the right thing to do if it maximizes happiness. Beginning with this ethical structure, they would then apply it to specific cases such as nuclear weapons. The correct action would be whatever maximizes happiness.

2.     Casuistry

In contrast, a bottom-up approach (or casuistry) gives priority to the action and makes the theory secondary. This approach relies on a person’s intuition to a scenario. For example, a person could begin by looking at the use of nuclear weapons at Hiroshima. They may have an intuition that it was wrong for the bomb to have been dropped due to the number of innocent civilians killed. They then may proceed to look at theories and principles that match their intuition. In the case of nuclear weapons, a person may turn to just war theory and the principle of discrimination that states it is wrong to target civilian bystanders.

3.     Reflexive Equilibrium

The final approach is reflexive equilibrium. This is where neither the philosophical theory nor intuition takes priority but instead are used to balance each other. It acknowledges that a person has a series of principles but also a series of intuitions about particular cases. For example, a person may believe in the principle that innocent civilians should never be killed in warfare. However, when confronted with the case of Hiroshima, they may have the intuition that it was the correct thing to do because they believe it prevented the deaths of many more people. The person then may change their principle to make exceptions in extreme scenarios where it is clear that it would save a large number of people.

Three Theories Commonly Applied to Nuclear Warfare

There are three, core ethical theories that are commonly used for the ethics of nuclear warfare. These are utilitarianism, deontology and just war theory.

1. Utilitarianism

The first and most commonly used, unsurprisingly, is utilitarianism. Utilitarianism is a consequentialist theory, which argues that whether an action is morally good or not is dependent on the consequences it brings about. In the case of utilitarianism, this is where the action brings about maximum happiness. When applied to nuclear ethics, whether launching an nuclear weapon is good or not is dependent on whether it brings about the most happiness.

2. Deontology

The second theory is deontology. Deontology is a non-consequentialist theory, which is when the morality of the action is not determined by the consequences that it brings about. In the case of deontology, this consists of following a predetermined set of rules that can be discovered through reason. The most common version of deontology is Kantian deontology, which holds that any moral rule needs to be universalizable and treats everyone as an end in themselves rather than a means to an end (this will be explained further later). Thus, whether launching a nuclear weapon is morally good or not is whether it follows the rules set out by deontology.

3. Just War Theory

The final theory is just war theory.  Just war theory initially started within a religious context but has expanded out to secular versions. The theory attempts to reconcile the principles that taking innocent human life is wrong while acknowledging that a state has a duty to defend its citizens and that sometimes this defense necessarily involves brute force. It thus prescribes the conditions of when a war would be permissible by focusing on two areas – jus ad bellum (the conditions under which war is justified) and jus in bello (how to conduct war in an ethical manner). Whether launching a nuclear weapon is morally good or not is whether it follows these principles.

Three Possible Positions on Nuclear Weapons

There are two distinctions that are prominent in nuclear ethics. When combined, they create three possible ethical stances to nuclear weapons.

1. Absolute vs Consequential

The first distinction that affects the approaches that can be taken to nuclear weapons is the absolute vs consequentialist distinction.

To be an absolutist is to hold there is never a scenario where nuclear weapons should be used. There can never be a scenario that justifies the use of nuclear weapons. Even if the use of nuclear weapons would save many lives in the long term, it would still be wrong to use them. It is inherently wrong, even if it is merely to be used as a deterrent.

Consequentialism, on the other hand, argues that there are some circumstances that could justify the use of nuclear weapons. For example, a person may think that it is reasonable to use a nuclear weapon when a number of lives could be saved in the long run. It should be noted that this is a slightly different definition to the one presented earlier to describe utilitarianism. It can both be used as a way to categorise normative theories and describe when there are circumstances that could justify an action.

Active Use vs Deterrence

Another distinction has been drawn between the active use of nuclear weapons and having nuclear weapons as a deterrence. To use nuclear weapons as a deterrence is to keep nuclear weapons, not necessarily to use on other states but instead to prevent nuclear weapons being used on your own state. This position arises from mutually assured destruction. If you possess nuclear weapons, then it means you can retaliate if someone attempts to use nuclear weapons on you. However, it also means you are unable to use nuclear weapons because the same would happen back.

Combining Absolutism, Consequentialism, Active Use and Deterrence

From these two distinctions, three positions to the ethics of nuclear weapons can be generated.

  1. Active use of nuclear weapons and their use as a deterrent is never morally permissible.
  2. Active use of nuclear weapons is never morally permissible, but it is sometimes morally permissible to use them as a deterrent.
  3. There are some circumstances that would make the active use of nuclear weapons morally permissible.

Conclusion and Next Steps

This blog post provided an introduction to applied ethics and nuclear weapons. It has discussed what applied ethics is, how to approach applied ethics, common theories applied to nuclear weapons and three different moral positions that may be taken to the ethics of nuclear weapons. The next post will begin to dive into detail by exploring utilitarianism, its relationship to nuclear weapons and whether it can truly be used to justify the bombing of Japan at the end of the Second World War.

Further Reading and References for Series So Far

Allhoff, Fritz. 2011. “What Are Applied Ethics?” Science and Engineering Ethics 17 (1): 1–19.

“Antinuclear Movement | History, Activism & Impact | Britannica.” 2023. August 9, 2023.

“Applied Ethics.” n.d. Ethics Unwrapped. Accessed August 14, 2023.

“Are Nuclear Weapons Useful?” n.d. Accessed July 24, 2023.

“Arms Race | Examples, Consequences, & Models | Britannica.” n.d. Accessed August 28, 2023.

“Atomic Bomb: Nuclear Bomb, Hiroshima & Nagasaki.” 2022. HISTORY. November 9, 2022.

“BBC – Ethics – War: Just War – Introduction.” n.d. Accessed September 12, 2023.

BBC News. 2020. “Nuclear Weapons: Which Countries Have Them and How Many Are There?,” January 14, 2020, sec. Newsbeat.

Bigg, Matthew Mpoke. 2023. “How Russia’s War in Ukraine Has Unfolded, Month by Month.” The New York Times, February 24, 2023, sec. World.

Churchill, Robert P. 1983. “Nuclear Arms as a Philosophical and Moral Issue.” The Annals of the American Academy of Political and Social Science 469: 46–57.

“Cuban Missile Crisis – Causes, Timeline & Significance.” 2023. HISTORY. April 20, 2023.

“Deontological Ethics | Definition, Meaning, Examples, & Facts | Britannica.” 2023. August 17, 2023.

“Deontology.” n.d. Ethics Unwrapped. Accessed September 6, 2023.

“Deterrence or Disarmament?: The Ethics of Nuclear Warfare.” n.d. Accessed July 24, 2023.

“Ethics.” n.d. Ethics Unwrapped. Accessed September 12, 2023.

Extra History, dir. 2018. Cuban Missile Crisis – The Failed Checkmate – Extra History – #1.

“‘Father of the Atomic Bomb’ Was Blacklisted for Opposing H-Bomb.” 2023. HISTORY. May 16, 2023.

Fisher, Richard. 2020. “Can Nuclear War Be Morally Justified?” News. BBC Future. 2020.

Frum, David. 2015. “The Cold War Never Really Ended.” The Atlantic. June 23, 2015.

Granoff, Jonathan. 1999. “Nuclear Weapons, Ethics, Morals and Law.” Nuclear Age Peace Foundation (blog). May 26, 1999.


Iskander, George. n.d. “The Manhattan Project Shows Scientists’ Moral and Ethical Responsibilities.” Scientific American. Accessed July 24, 2023.

“Just War Theory | Internet Encyclopedia of Philosophy.” n.d. Accessed September 12, 2023.

Krol, John Cardinal. 1983. “The Catholic Bishops’ Concern with Nuclear Armaments.” The Annals of the American Academy of Political and Social Science 469: 38–45.

Lackey, Douglas P. 1985. “Immoral Risks: A Deontological Critique of Nuclear Deterrence.” Social Philosophy and Policy 3 (1): 154–75.

Leach, Stephen. 2022. “Philosophy and Nuclear Weapons.” March 18, 2022.

Malik, Kenan. 2020. “Don’t Let the Victors Define Morality – Hiroshima Was Always Indefensible.” The Observer, August 9, 2020, sec. Opinion.

McMahan, Jeff. 1985. “Deterrence and Deontology.” Ethics 95 (3): 517–36.

@NatGeoUK. 2019a. “The Chernobyl Disaster: What Happened, and the Long-Term Impact.” National Geographic. May 20, 2019.

———. 2019b. “The Chernobyl Disaster: What Happened, and the Long-Term Impact.” National Geographic. May 20, 2019.

“Pearl Harbor: Attack, Deaths & Facts.” 2022. HISTORY. December 6, 2022.

published, Tom Metcalfe. 2022. “What Is Mutual Assured Destruction?” Livescience.Com. March 18, 2022.

Quinlan, Michael. 2009a. “5 The Ethics of Nuclear Weapons.” In Thinking About Nuclear Weapons: Principles, Problems, Prospects, edited by Michael Quinlan, 0. Oxford University Press.

———. 2009b. Thinking About Nuclear Weapons: Principles, Problems, Prospects. 1st ed. Oxford University PressOxford.

Roman Styran, dir. 2017. Bertrand Russell – Press Conference on Nuclear Weapons – Caxton Hall, London, 9 July 1955.

“Russell-Einstein Manifesto – Nuclear Museum.” n.d. Https://Ahf.Nuclearmuseum.Org/ (blog). Accessed August 22, 2023.

Seidel, Jamie. 2023. “‘Pressure Is Mounting’: Europe Rocked by Horrifying Russian Nuclear Weapons Claim.” News.Com.Au, August 23, 2023, sec. Military.

Shaw, William H. 1984. “Nuclear Deterrence and Deontology.” Ethics 94 (2): 248–60.

Shephard, Ben. 2012. “Inside the Centre: The Life of J Robert Oppenheimer by Ray Monk – Review.” The Observer, December 16, 2012, sec. Books.

Stevenson, Leslie. 1986. “Is Nuclear Deterrence Ethical?” Philosophy 61 (236): 193–214.

“The Crew of the <em>Enola Gay</Em> on Dropping the Atomic Bomb.” 2015. Mental Floss. August 6, 2015.

“The History of Britain’s Nuclear Weapons.” n.d. Imperial War Museums. Accessed August 22, 2023.

“The Nuclear Dilemma: The Greatest Moral Problem of All Time.” n.d. Accessed July 24, 2023.

“Utilitarianism | Definition, Philosophy, Examples, Ethics, Philosophers, & Facts | Britannica.” n.d. Accessed August 16, 2023.

Van Munster, Rens. 2023. “Nuclear Weapons, Existentialism, and International Relations: Anders, Ballard, and the Human Condition in the Age of Extinction.” Review of International Studies, January, 1–19.

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