Hostname: page-component-848d4c4894-ttngx Total loading time: 0 Render date: 2024-05-20T12:07:57.068Z Has data issue: false hasContentIssue false

Should Weaponised Moral Enhancement Replace Lethal Aggression in War?

Published online by Cambridge University Press:  17 March 2023

Joao Fabiano*
Visiting Fellow, Ash Center for Democratic Governance and Innovation, Harvard University, United States; Post-doctoral Fellow, Department of Philosophy, University of Sao Paulo, Brazil.
Get access


Some have proposed the development of technologies that improve our moral behaviour – moral enhancement – in order to address global risks such as pandemics, global warming and nuclear war. I will argue that this technology could be weaponised to manipulate the moral dispositions of enemy combatants. Despite being morally controversial, weaponised moral enhancement would be neither clearly prohibited nor easily prohibitable by international war law. Unlike previous psychochemical weapons, it would be relatively physically harmless. I argue that when combatants are liable to lethal aggression to achieve an aim of war, they are also liable to weaponised moral enhancement to achieve that same aim. Weaponised moral enhancement will loosen just war requirements in both traditional and revisionist normative just war theories. It will particularly affect revisionist theories’ jus ad bellum requirements for humanitarian and preventive wars. For instance, weaponised moral enhancement could be more proportional and efficacious than lethal aggression to effect institutional changes in preventive and humanitarian wars. I will conclude that, despite evading international war laws and loosening normative just war requirements, the intuition that weaponised moral enhancement would gravely harm combatants can be defended by arguing that it would severely disturb personal identity, which could potentially ground future prohibitions.

Copyright © The Author(s), 2023. Published by Cambridge University Press in association with the Faculty of Law, the Hebrew University of Jerusalem

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)


1 Crockett, Molly J and others, ‘Serotonin Selectively Influences Moral Judgment and Behavior through Effects on Harm Aversion’ (2010) 107 Proceedings of the National Academy of Sciences 17433CrossRefGoogle ScholarPubMed.

2 Decreasing serotonin had the opposite effect in another study: Crockett, Molly J and others, ‘Serotonin Modulates Behavioral Reactions to Unfairness’ (2008) 320 Science 1739CrossRefGoogle ScholarPubMed.

3 Crockett, Molly J, ‘Moral Bioenhancement: A Neuroscientific Perspective’ (2014) 40 Journal of Medical Ethics 370CrossRefGoogle ScholarPubMed.

4 Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction (entered into force 29 April 1997) 1974 UNTS 45.

5 Hague Convention (IV) respecting the Laws and Customs of War on Land and its Annex: Regulations concerning the Laws and Customs of War on Land (entered into force 26 January 1910) Martens Nouveau Recueil (ser 3) 461, preamble.

6 Persson, Ingmar and Savulescu, Julian, Unfit for the Future: The Need for Moral Enhancement (Oxford University Press 2012)CrossRefGoogle Scholar.

7 Douglas, Thomas, ‘Moral Enhancement’ (2008) 25 Journal of Applied Philosophy 228CrossRefGoogle ScholarPubMed.

8 Bilderbeck, Amy C and others, ‘Serotonin and Social Norms: Tryptophan Depletion Impairs Social Comparison and Leads to Resource Depletion in a Multiplayer Harvesting Game’ (2014) 25 Psychological Science 1303CrossRefGoogle Scholar; De Dreu, Carsten KW and Kret, Mariska E, ‘Oxytocin Conditions Intergroup Relations through Upregulated In-Group Empathy, Cooperation, Conformity, and Defense’ (2016) 79 Biological Psychiatry 165CrossRefGoogle ScholarPubMed; Krueger, Frank and others, ‘Oxytocin Selectively Increases Perceptions of Harm for Victims but not the Desire to Punish Offenders of Criminal Offenses’ (2013) 8 Social Cognitive and Affective Neuroscience 494CrossRefGoogle Scholar; Tse, Wai S and Bond, Alyson J, ‘Serotonergic Intervention Affects Both Social Dominance and Affiliative Behaviour’ (2002) 161 Psychopharmacology 324CrossRefGoogle ScholarPubMed; Wood, Richard M and others, ‘Effects of Tryptophan Depletion on the Performance of an Iterated Prisoner's Dilemma Game in Healthy Adults’ (2006) 31 Neuropsychopharmacology 1075CrossRefGoogle ScholarPubMed; De Dreu, Carsten KW, ‘Oxytocin Modulates Cooperation within and Competition between Groups: An Integrative Review and Research Agenda’ (2012) 61 Hormones and Behavior 419CrossRefGoogle ScholarPubMed; Kosfeld, Michael and others, ‘Oxytocin Increases Trust in Humans’ (2005) 435 Nature 673CrossRefGoogle ScholarPubMed; Fischer-Shofty, Meytal and others, ‘Improving Social Perception in Schizophrenia: The Role of Oxytocin’ (2013) 146 Schizophrenia Research 357CrossRefGoogle ScholarPubMed; Crockett and others (n 1); Crockett and others (n 2). For an overview of how social behaviour can be manipulated by pharmacology see Crockett, Molly J and Fehr, Ernst, ‘Pharmacology of Economic and Social Decision Making’ in Glimcher, Paul W and Fehr, Ernst (eds), Neuroeconomics (2nd edn, Elsevier 2014) 259Google Scholar.

9 Levy, Neil and others, ‘Are You Morally Modified? The Moral Effects of Widely Used Pharmaceuticals’ (2014) 21 Philosophy, Psychiatry, and Psychology 111CrossRefGoogle ScholarPubMed.

10 Agar, Nicholas, ‘Moral Bioenhancement Is Dangerous’ (2015) 41 Journal of Medical Ethics 343Google Scholar; Harris, John, ‘“Ethics Is for Bad Guys!” Putting the “Moral” into Moral Enhancement’ (2013) 27 Bioethics 169CrossRefGoogle ScholarPubMed. These authors are also sceptical of the near future feasibility of moral enhancement, an issue I will not address here. A reasonable chance that we will attempt to develop these technologies is sufficient motivation for my considerations. The many studies cited at n 8 support that modest claim. Moreover, moral enhancement would not violate any known natural law; hence, it is at least physically possible.

11 Joao Fabiano, ‘The Fragility of Moral Traits to Technological Interventions’ (2021) 14 Neuroethics 269.

12 John Pike, ‘AGM-114 R9X Hellfire Blade Bomb’, Global Security, 17 May 2019,

13 The needed broad psychological deterrence has been defined as ‘preventing action by either direct or indirect influence on psychology … which consists in considering all those states of the mind/brain information processing system that influence action, be they conscious or not, be they rational or not, be they distributed across an organization or not’: Troy S Thomas and William D Casebeer, ‘Violent Systems: Defeating Terrorists, Insurgents, and Other Non-State Adversaries’, Institute for National Security Studies Occasional Paper 52, March 2004, 54–55. Weaponised moral enhancement would clearly fall into this category.

14 A white paper from the US Army states: ‘It is vital to develop an understanding of … how existing or new neuroscientific techniques and neurotechnologies could be used and developed to facilitate improved evaluative and interventional capability’: William D Casebeer and others, ‘Neurobiological, Cognitive and Social Science Insights on Radicalization and Mobilization to Violence’ in M Hardenberg (ed), National Security Challenges: Insights from Social, Neurobiological, and Complexity Sciences (SMA and US Army ERDC White Papers 2012) 198. An academic article on neuroweapons considers: ‘A considerably more imposing possibility is to “change minds and hearts” by altering the will or capacity to fight through the use of neuropharmacologic, neuromicrobiological and/or neurotoxic agents that 1) mitigate aggression and foster cognitions and emotions of affiliation or passivity’: James Giordano and Rachel Wurzman, ‘Neurotechnologies as Weapons in National Intelligence and Defense – An Overview’ (2011) 2 Synesis: A Journal of Science, Technology, Ethics, and Policy 55, 59.

15 Neta C Crawford, ‘The U.S. Budgetary Costs of the Post-9/11 Wars’, Watson Institute for International and Public Affairs and Brown University, 1 September 2021,; Amy Hagopian and others, ‘Mortality in Iraq Associated with the 2003–2011 War and Occupation: Findings from a National Cluster Sample Survey by the University Collaborative Iraq Mortality Study’ (2013) 10 PLOS Medicine, article e1001533.

16 See n 17 for death tolls. For other motivations see n 67. For the humanitarian motivations see James M McPherson, Battle Cry of Freedom: The Civil War Era (Oxford University Press 2003) vii–viii, 490–510, 546–67 (McPherson (2003)); James M McPherson, ‘The War Will Never End Until We End Slavery’ in James M McPherson, What They Fought For, 1861–1865 (Louisiana State University Press 1994) 47, 47–48; Edward B Rugemer, ‘Emancipation Day Traditions in the Anglo-Atlantic World’ in Gad Heuman and Trevor Burnard (eds), The Routledge History of Slavery (Routledge 2010) 314, 324–25; Jason H Silverman, ‘Civil War, United States’ in Junius P Rodriguez (ed), The Historical Encyclopedia of World Slavery (ABC-CLIO 1997) 157; Paul Finkelman, ‘United States, Antislavery In’ in Peter Hinks, John McKivigan and R Owen Williams (eds), Encyclopedia of Antislavery and Abolition (Greenwood Press 2007) 704, 713–15; Seymour Drescher, Abolition: A History of Slavery and Antislavery (Cambridge University Press 2009) 322–32; David Brion Davis, Inhuman Bondage: The Rise and Fall of Slavery in the New World (Oxford University Press 2006) Ch 15, 297; Robert William Fogel, Without Consent or Contract: The Rise and Fall of American Slavery (Norton 1994) 411–17; John Stauffer, ‘ Abolition and Antislavery’ in Mark M Smith and Robert L Paquette (eds), Oxford Handbook of Slavery in the Americas (Oxford University Press 2012) 556, 571–75.

17 J David Hacker and James M McPherson, ‘A Census-Based Count of the Civil War Dead: With Introductory Remarks by James M. McPherson’ (2011) 57 Civil War History 307; James T Patterson, Grand Expectations: The United States, 1945–1974 Vol 4 (Oxford University Press 1998) 10.

18 De Dreu (n 8); Sylvia Terbeck and others, ‘Propranolol Reduces Implicit Negative Racial Bias’ (2012) 222 Psychopharmacology 419.

19 Turhan Canli and others, ‘Neuroethics and National Security’ (2007) 7 The American Journal of Bioethics 3; William Casebeer, ‘Ethics and the Biologized Battlefield: Moral Issues in 21st-Century Conflict’ in Robert E Armstrong and others (eds), Bio-inspired Innovation and National Security (National Defense University Press 2010) 293, 299–302.

20 See end of Section 5.1 for additional discussion on advanced incapacitating agents.

21 My definition of weaponised moral enhancement applies the seminal definition of moral enhancement by Tom Douglas to the case of using it as a war weapon. Although Douglas’ definition is often used in the literature, moral enhancement has been defined in many other ways. That is not in itself a problem if each definition is made explicit. For the many definitions of moral enhancement see Kasper Raus and others, ‘On Defining Moral Enhancement: A Clarificatory Taxonomy’ (2014) 7 Neuroethics 263. For the seminal definition see Douglas (n 7).

22 Nevertheless, one might object that my definition implies a coercive use of moral enhancement, which would be self-defeating. Firstly, weaponised moral enhancement would be no more coercive than conventional lethal weapons. Secondly, harm to freedom could be outweighed by enhancing moral reasoning and decision making such that there would be an overall increase of freedom of choice. This issue has been discussed extensively in the literature but will not be investigated further here. See David DeGrazia, ‘Moral Enhancement, Freedom, and What We (Should) Value in Moral Behaviour’ (2014) 40 Journal of Medical Ethics 361; Thomas Douglas, ‘Enhancing Moral Conformity and Enhancing Moral Worth’ (2014) 7 Neuroethics 75; Julian Savulescu and Ingmar Persson, ‘Moral Enhancement, Freedom, and the God Machine’ (2012) 95 The Monist 399.

23 My list is of mere instrumental value in order to discuss a yet non-existent weapon. It is a plain summary of often-mentioned basic principles. Because of space limitations, I will not assess the impact of alternative principles on my arguments. For similar lists, see Robert Kolb and Richard Hyde, An Introduction to the International Law of Armed Conflicts (Hart 2008) 43–50; Seth Lazar, ‘War’ in Edward N Zalta (ed), The Stanford Encyclopedia of Philosophy (Stanford University 2020),; ICJ, Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion [1996] ICJ Rep 1 226, [78]; Larry May, ‘Introduction’ in Larry May (ed), The Cambridge Handbook of the Just War (Cambridge University Press 2018); Jeff McMahan, ‘The Morality of War and the Law of War’ in David Rodin and Henry Shue (eds), Just and Unjust Warriors: The Moral and Legal Status of Soldiers (2nd edn, Oxford University Press 2013) 19; US Department of Defense, Department of Defense Law of War Manual (Office of General Counsel, Department of Defense 2016) 38–52.

24 Michael Walzer, Just and Unjust Wars: A Moral Argument with Historical Illustrations (4th edn, Basic Books 2006) 41. A detailed definition or proper translation of jus ad bellum and jus in bello are beyond the scope of this article. Although the current legal meaning of jus is often restricted to ‘right’ or ‘law’, ‘justice’ is an alternative translation of this Latin word; see Peter Glare (ed), ‘Ius’ in Oxford Latin Dictionary (Oxford University Press 2012) 1082–84; Michael Hillen (ed), ‘Ius’ in Thesaurus Linguae Latinae, Vol VII-2 (Bavarian Academy of Sciences and Humanities 2019) 678–704; Jonathan Law (ed), ‘Jus’ in A Dictionary of Law (Oxford University Press 2022); William Whitaker (ed), ‘Jus’ in WORDS (University of Notre Dame 2016),

25 I will treat necessity as included in proportionality of means. Although these are often mentioned as separate requirements, they are both included in the requirement that means must minimise the net amount of harm in proportion to the good achieved. Moreover, a third principle is often mentioned as justifying necessity and proportionality: the overarching principle of humanity. Given that the meaning of such a principle is unclear, and I wish to avoid equating it with necessity and proportionality, I will discuss some prohibitions from the principle of humanity separately in Section 5.2. See also William H Boothby, Weapons and the Law of Armed Conflict, Vol 1 (2nd edn, Oxford University Press 2016) 46.

26 Charter of the United Nations (entered into force 24 October 1945) 1 UNTS XVI, arts 2(4), 51.

27 Hague Convention (II) with respect to the Laws and Customs of War on Land and its Annex: Regulations concerning the Laws and Customs of War on Land (entered into force 4 September 1900) 26 Martens Nouveau Recueil (ser 2) 949, art 23(e); Hague Convention (IV) (n 5) art 23(e); Convention on Prohibitions or Restrictions on the Use of Certain Conventional Weapons which may be deemed to be Excessively Injurious or to have Indiscriminate Effects, Protocol II on Prohibitions or Restrictions on the Use of Mines, Booby-Traps and Other Devices (entered into force 2 December 1983) 1342 UNTS 137, preamble; Declaration Renouncing the Use, in Time of War, of Explosive Projectiles Under 400 Grammes Weight (entered into force 11 December 1868); Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts (entered into force 7 December 1978) 1125 UNTS 3 (AP I), art 35(2); US Department of Defence (n 23) 316–34.

28 Nuclear Weapons (n 23) [78].

29 Jean-Marie Henckaerts and Louise Doswald-Beck (eds), Customary International Humanitarian Law Vol 1: Rules, (International Committee of the Red Cross and Cambridge University Press 2005, revised 2009) (ICRC Study) 237.

30 Convention on the Prohibition of the Development, Production and Stockpiling of Bacteriological (Biological) and Toxin Weapons and on their Destruction (entered into force 25 March 1975) 1015 UNTS 165; United Nations Office for Disarmament Affairs, UNGA, ‘Final Declaration of the Fourth Review Conference of the Parties to the Convention on the Prohibition of the Development, Production and Stockpiling of Bacteriological (Biological) and Toxin Weapons and on Their Destruction’, United Nations Disarmament Yearbook 1996 (UN 1997).

31 World Health Organization Group of Consultants, ‘Health Aspects of Chemical and Biological Weapons’, Report EB45.R17, 28 November 1969, 12.

32 (n 4) art II.2.

33 ibid art II.7.

34 ibid art II.9.

35 Malcolm Dando and Martin Furmanski, ‘Mid-Spectrum Incapacitant Programs’ in Mark Wheelis (ed), Deadly Cultures: Biological Weapons since 1945 (Harvard University Press 2006) 236, 243–44; Robert J Mathews, ‘Central Nervous System-Acting Chemicals and the Chemical Weapons Convention: A Former Scientific Adviser's Perspective’ (2018) 90 Pure Applied Chemistry 1559.

36 Alan Pearson, ‘Incapacitating Biochemical Weapons: Science, Technology, and Policy for the 21st Century’ (2006) 13 The Nonproliferation Review 151.

37 Mark Wheelis and Malcom Dando, ‘Neurobiology: A Case Study of the Imminent Militarization of Biology’ (2005) 87 International Review of the Red Cross 553, 567.

38 ICRC, ‘Expert Meeting: “Incapacitating Chemical Agents” – Law Enforcement, Human Rights Law and Policy Perspectives’, 24–26 April 2012, 153.

39 ECtHR, Finogenov and Others v Russia, App Nos 18299/03 and 27311/03, 20 December 2011, paras 227–36.

40 Boothby (n 25) 126–31; ICRC Expert Meeting (n 38) 157; Pearson (n 36); Neil Davison, ‘New Weapons: Legal and Policy Issues Associated with Weapons Described as “Non-Lethal”’ in Andrew D Saxon (ed), International Humanitarian Law and the Changing Technology of War (Martinus Nijhoff 2013) 279, 306–07; Wheelis and Dando (n 37).

41 Robin M Coupland and Peter Herby, ‘Review of the Legality of Weapons: A New Approach – The SirUS Project’ (1999) 81 International Review of the Red Cross 583, 587–88.

42 Donna M Verchio, ‘Just Say No! The SIrUS Project: Well-Intentioned, but Unnecessary and Superfluous’ (2001) 51 Air Force Law Review 183.

43 Hague IV (n 5) preamble.

44 The original intention of the Martens Clause, its true legal meaning, its impact on international war law and what it justifies have been extensively discussed in the literature. Most accept that the clause denies that if something is not prohibited by specific laws, it is allowed. The clause states that customary laws, laws of humanity and the dictates of public conscience can still prohibit conduct not covered by existing laws. There is no consensus on whether these additional principles should guide new laws, specify a new body of laws, or are merely an interpretative guide for existing laws. For a history of the use and interpretations of the Martens Clause, see Jochen von Bernstorff, ‘Martens Clause’, Max Planck Encyclopedia of Public International Law (Oxford University Press 2009); Antonio Cassese, ‘The Martens Clause: Half a Loaf or Simply Pie in the Sky?’ (2000) 11 European Journal of International Law 187; Theodor Meron, ‘The Martens Clause, Principles of Humanity, and Dictates of Public Conscience’ (2000) 94 American Journal of International Law 78; Mitchell Stapleton-Coory, ‘The Enduring Legacy of the Martens Clause: Resolving the Conflict of Morality in International Humanitarian Law’ (2019) 40 Adelaide Law Review 471.

45 I focus on the salient issue of psychological coercion, but it is plausible that weaponised moral enhancement violates humanitarian principles in other ways that are still unexplored. For example, it is possible that the harm to personal identity explored in Section 7.1 could constitute a humanitarian violation. However, because of the open-ended nature of the Martens Clause, scope limitations preclude a thorough investigation of these matters, which merit a separate article.

46 Nuclear Weapons (n 23) [95] and [105]. Judge Guillaume's separate opinion states that the Court implicitly recognised the legality of deterrence: ibid [9]. For the often-ignored non-nuclear deterrence doctrine behind vast standing armies see John J Mearsheimer, Conventional Deterrence (Cornell University Press 1985).

47 (n 26) arts 2(4), 51.

48 UNGA Res 11/1, Aggression against Ukraine (2 March 2022), UN Doc A/RES/ES-11/1; UNGA Res 11/2, Human Consequences of the Aggression against Ukraine (24 March 2022), UN Doc A/RES/ES-11/2; UNGA Res ES-11/3, Suspension of the Rights of Membership of the Russian Federation in the Human Rights Council (7 April 2022), UN Doc A/RES/ES-11/3.

49 Three different datasets with 212, 158 and 64 instances of use of force by the US from 1937 to 2002 contain, respectively, 167 (79%), 92 (58%) and 28 (44%) unilateral uses of force – averaging at two thirds. In all three datasets the frequency of unilateral use never went below one third for any time period or president: Bradley F Podliska, Acting Alone: A Scientific Study of American Hegemony and Unilateral Use-of-Force Decision Making (Lexington 2010) 4.

50 Rome Statute of the International Criminal Court (entered into force 1 July 2002) 2187 UNTS 90.

51 US Department of Defense (n 23) 1125–27.

52 Sven Pöhle, ‘Germany a Hub for US Drone War?’, Deutsche Welle, 5 April 2014, The community around the base houses over 50,000 US personnel and family. There are over 100,000 US military personnel stationed in Europe in total, which is over half of the total German military personnel: ‘Personalzahlen der Bundeswehr’, Bundeswehr, 31 March 2022,; US Department of Defense, Military Installations, ‘USAG Rheinland-Pfalz Kaiserslautern Military Community’, 2022,; Kathleen J McInnis, Paul Belkin and Brendan W McGarry, ‘United States European Command: Overview and Key Issues’, Congressional Research Service, 30 March 2022.

53 Podliska (n 49).

54 Seth Carus, A Short History of Biological Warfare: From Pre-History to the 21st Century (National Defense University Press 2017) 47.

55 Seth Lazar, ‘Evaluating the Revisionist Critique of Just War Theory’ (2017) 146 Daedalus 113; Lazar (n 23); David Rodin and Henry Shue, ‘Introduction’ in Rodin and Shue (n 23) 1.

56 Jeff McMahan, Killing in War (Oxford University Press 2009) 15.

57 Jeff McMahan, ‘Just Cause for War’ (2005) 19 Ethics and International Affairs 1, 5.

58 Allen Buchanan and Robert O Keohane, ‘The Preventive Use of Force: A Cosmopolitan Institutional Proposal’ (2004) 18 Ethics and International Affairs 1; Jeff McMahan, ‘Preventive War and the Killing of the Innocent’ in Richard Sorabji and David Rodin (eds), The Ethics of War: Shared Problems in Different Traditions (Ashgate 2006); Jeff McMahan, ‘Précis: The Morality and Law of War’ (2007) 40 Israel Law Review 670, 680–81.

59 This is a distinctively revisionist way of phrasing the question, centred around individual moral liability. Some traditionalists have combatant equality as a basic principle requiring little explanation; some justify it with the pragmatical concerns that absent combatant equality both sides would consider themselves just, and fight without any restraint: eg Yuval Shany, ‘A Pragmatic Objection to Moral Distinctions: A Comment on the Morality and Law of War’ (2007) 40 Israel Law Review 701, 707–09. Either way, as I will argue, if combatants are equally liable to killing, they are equally liable to lesser harm.

60 eg Walzer (n 24) 34–41.

61 eg McMahan (n 23) 20–22.

62 Thomas Douglas, ‘Nonconsensual Neurocorrectives and Bodily Integrity: A Reply to Shaw and Barn’ (2019) 12 Neuroethics 107.

63 eg CA Penal Code § 645 (2019); FL Statutes § 794.0235 (2003); Iowa Code § 903B.10 (2003).

64 The conditional nature of the argument means that it will remain valid in a wide range of in bello requirements; including less or more strict versions of proportionality of means, as I have presented in Section 4. As long as goods must outweigh types of harm, liability to lethal aggression will imply liability to weaponised moral enhancement.

65 Although prevention cannot be a just cause for war for traditionalists, being attacked can give just cause for a war the aim of which is to prevent future attacks.

66 Buchanan and Keohane (n 58); McMahan (2006) (n 58).

67 Allen Buchanan, Our Moral Fate: Evolution and the Escape from Tribalism (The MIT Press 2020) Ch 1.

68 The war killed 2.4% of the US population and used particularly gruesome tactics such as the Atlanta and South Carolina Campaigns’ total destruction and the Battle of the Crater's futile massacres of blacks (Albert Castel, Decision in the West: The Atlanta Campaign of 1864 (University Press of Kansas 1992); Suderow, Bryce A, ‘The Battle of the Crater: The Civil War's Worst Massacre’ (1997) 43 Civil War History 219CrossRefGoogle Scholar; McPherson (n 16) 807–30; Hacker and McPherson (n 17). Regardless of the justice (and injustice) of and in the American Civil War by each side, subsequent US history indicates that wars can fail to address significantly the underlying exclusivist moralities that enable humanitarian violations. In fact, in so far as perceived environmental scarcity fosters exclusivist moralities, post-war conditions can exacerbate the problem. Such considerations are weighty, but not overwhelming, in evaluating preventive causes for war, but less so elsewhere. The American Civil War also had defensive and humanitarian causes (eg defending against Confederate aggression and stopping ongoing slavery), besides civil matters out of scope – see n 16 for references on humanitarian causes. Even in so far as it had preventive causes, preventing one of most atrocious violations of human rights in recorded history could have justified a decisively aggressive response. Interestingly, while provisionally framing it as a defensive war by the Union, Walzer uses the Atlanta Campaign as the primary example of a just war fought without just restraint: Walzer (n 24) 32–33). For the US racially exclusivist institutions of the Jim Crow Era see Patterson (n 17) 375–406.

69 David Lewis, ‘Survival and Identity’, Philosophical Papers, Vol 1 (Oxford University Press 1983) 55; Derek Parfit, Reasons and Persons (Oxford University Press 1984) 196; Jeff McMahan, The Ethics of Killing (Oxford University Press 2002) 39.

70 Lewis (n 69).

71 ibid 65–67.

72 Strohminger, Nina and Nichols, Shaun, ‘The Essential Moral Self’ (2014) 131 Cognition 159CrossRefGoogle ScholarPubMed.

73 Fabiano (n 11); Fabiano, Joao, ‘Persons vs. Supra-Persons and the Undermining of Individual Interests’ (2021) The Journal of Value InquiryCrossRefGoogle Scholar.

74 Crutchfield, Parker, ‘Moral Enhancement Can Kill’ (2018) 43 The Journal of Medicine and Philosophy: A Forum for Bioethics and Philosophy of Medicine 568CrossRefGoogle ScholarPubMed.

75 In a different scenario, many patients with degenerative cognitive conditions, such as Alzheimer's, sign a ‘Do Not Resuscitate’ order because they would rather die than continue to live with a severely compromised mental life, despite that life does not necessarily involve additional suffering. If moral psychology is indeed the core of personal identity, a severely compromised moral life would be even less worth living.

76 Bornstein, Gary, ‘Intergroup Conflict: Individual, Group, and Collective Interests’ (2003) 7 Personality and Social Psychology Review 129CrossRefGoogle ScholarPubMed.

77 Boyd, Robert and others, ‘The Evolution of Altruistic Punishment’ (2003) 100 Proceedings of the National Academy of Sciences 3531CrossRefGoogle ScholarPubMed; Crockett and others (n 2).

78 Begue, Laurent and others, ‘Personality Predicts Obedience in a Milgram Paradigm’ (2015) 83 Journal of Personality 299CrossRefGoogle Scholar.