#175 Conscience, Scripture, and Divine Justice in the Application of Just War Theory

Abstract

The purpose of this paper is to show that just war theory, particularly Jus Ad Bellum, is useful and finds its basis in Scripture. While just war theory provides a framework for evaluating the morality of war, the Christian soldier bears an even deeper responsibility to conscience, Scripture, and divine justice, which may at times demand resistance to state commands in favor of higher moral obligations. When Just War Theory is applied to a specific situation the Christian soldier has several individual duties. The Christian soldier must decide for themselves if they are morally obligated to fight or to not fight on behalf of their country. What follows are Biblical examples of war, ethical implications of relevant texts, historical precedent, and then a consideration of case studies from World War Two, and the modern day American relevance.

Introduction to Paper

While just war theory provides a framework for evaluating the morality of war, the Christian soldier bears an even deeper responsibility to conscience, Scripture, and divine justice, which may at times demand resistance to state commands in favor of higher moral obligations. These deeper responsibilities in their true context are the foundations of just war theory. Just war theory is meaningless if the action in question is not properly evaluated by each individual involved through the lens of conscience, Scripture, and divine justice. The actions of the Christian soldier must be acceptable according to their own conscience which is the basis of the individual's moral actions. Each soldier must align their actions with what they know about the nature of what God has taught to His people in the Bible. While ensuring that their actions align with God’s divine justice and do not overstep the bounds set by God.

Interplay of Conscience, Scripture, and Divine Justice in Just War Theory

Conscience, Scripture, and divine justice are an integral part of just war theory. Each plays a distinct role in just war theory. Conscience is that thing which causes the individual soldier to fight or not to fight. Conscience is informed by the Holy Spirit and God’s Word. Scripture informs our actions and behaviors. While divine justice is the idea that God also has a part to play in war. Either to interfere or not to interfere for better or worse in the war. That God has His own sense of justice that must be satisfied but not infringed. Each of these add up practically to just war theory. Though properly just war theory is based primarily on Biblical Ethics.

Scope of Paper

This paper will focus mainly on how just war theory functions. There will be explorations into just war theory from multiple angles. Consideration of the effects of Biblical ethics and just war theory will be examined. Case studies into historical and modern examples of war will be considered through the lens of just war theory.

Introduction to Just War Theory and its Development Over Time

Just war theory has been developed over time by multiple groups and people with varying intentions. The foundations of just war theory are found in the writings of people like Plato and Cicero. That foundation was later built upon by the likes of Augustine and Aquinas. While in modern times these foundations have had many of their assumptions reconsidered because of the rise of democracy by the likes of Bonhoeffer and Barth.

Biblical War Ethics

Before just war theory was christianized by Augustine and Aquinas there was Biblical ethics from the Old and New Testaments which guided Christian thought and action. Today Biblical ethics underpins just war theory but expands on Biblical ethics by considering the practical implications of war. Biblical ethics in its infancy was formulated by conscience and direct relationship to God as can be seen in the example of Shadrach, Meshach and Abed-nego in Daniel 3:16-18 where they appeal to God and conscience.

Just War Theory Meets Christendom

The historical development of just war theory before it was injected by Biblical ethics can be seen in the writings of people like Plato and Cicero. The idea of war being good or bad is founded on the relationship between states and how that relationship ought to function. Plato wrote that “Every city is in a natural state of war with every other, not indeed proclaimed by heralds, but everlasting.” By which he explains that war is the natural process of resources moving between a stronger and weaker party. This may be called stealing if it were between two individuals. But at the scale of a city or state in Plato's eyes would be a proper redistribution of power and control that is not without its modern counterpart. Cicero wrote that “No war is considered just unless it has been proclaimed and declared, or unless reparation has first been demanded.” By Cicero’s day this idea had been developed such that there is a right order to actions in war. In this case negotiations precede war. But there are times now that this particular injunction is dismissed. As Clausewitz wrote about deciding to go to war, “The errors that proceed from a spirit of benevolence are the worst.” This may be taken to mean that the normal limits of just war theory in its traditional form may be broken in order to accomplish a swifter victory. This is evidently a good choice in war but it may also be the more moral choice at times as it spares unnecessary bloodshed.

Just War Theory Adopted by Christendom

Just war theory was later adopted by Christendom through Biblical ethics as Christianity became the dominant religion in the western world. This was a gradual process but one where Augustine takes over the idea of just war directly from Cicero” in his book The City of God. Augustine wrote “He, then, who prefers what is right to what is wrong, and what is well-ordered to what is perverted, sees that the peace of unjust men is not worthy to be called peace in comparison with the peace of the just.” Augustine then is making a claim that there is a sort of natural law not unlike that which Plato first mentioned that calls on nations to be the arbiters of what peace or justice will look like.

In turn Aquinas takes up the mantle in his Summa Theologica. Aquinas lays out the many reasons that war is completely unjust referencing verses like Matthew 26:52, Matthew 5:39, and Romans 12:19. But then he flips things around and shows how rather than outright ban war he gives a list of justifications of war and considers verses like Romans 13:4. He examples that war is to be carried out by the proper authority of the state rather than that of the individual. As the individual can take recourse to the state but the state has nowhere else to turn. In summary as Augustine wrote, “For what else is victory than the conquest of those who resist us? and when this is done there is peace. It is therefore with the desire for peace that wars are waged.” Just war is ultimately waged out of a love of peace and justice.

Bonhoeffer and Barth

Jumping ahead in history Bonhoeffer and Barth provide a new perspective of just war theory as they grappled with the control of the corrupt Nazi regime. Bonhoeffer notably rejected Aquinas’s notion that war is to only be carried out by those in power. Instead he attempted to assassinate Hitler. Again it may be observed in Bonhoeffer’s action the spirit of just war if not the letter of just war theory. In Bonhoeffer’s context the thing that would bring about the end of the war quickest could be understood to be the most just action and therefore the right action.

Bonhoeffer

Bonhoeffer understood the claim of government in a different way than Aquinas, he wrote “The claim of government, which is based on its power and its mission, is the claim of God and is binding upon conscience. Government demands obedience “for conscience’ sake” (Rom. 13.5).” This would mean that the individual soldier is subject to the will of the government so long as the government operates within its claim. Once the government rejects its claim to authority directly to the individual only then are they free to act as they see fit. Bonhoeffer continues that “Belief, conscience and bodily life are subject to an obligation of obedience with respect to the divine commission of government.” Put another way, the government acts as the god of a soldier, in so much as the soldier must obey, until the government rejects that claim by ordering an individual to go against their conscience and the conscience of the state.

Barth

On the other hand Karl Barth’s formulation on the justification of war was based on war as an extension of executions. Barth wrote that “War is the execution which a people organized as a state, on account of its will to live, performs on another people which threatens its will to live.” Therefore warfare is only acceptable to a Christian as it stands or falls in the justification of the legalization of executing an individual. With these boundaries in mind the Jus Ad Bellum, the decision to go to war, is greatly limited.

The Theological Declaration of Barmen

The Theological Declaration of Barmen acted as a declaration from the German church that the German government had betrayed its purpose. One of the main claims of the declaration was that the Nazi government had shifted the balance of power away from the church. Thereby corrupting the stabilizing influence of the church on the government. The authors of the Theological Declaration of Barmen included the like of Karl Barth, with input from Martin Niemöller, and Thomas Breit. Dietrich Bonhoeffer was also a supporter of the declaration. One of the statements from the declaration reads, “We reject the false doctrine, as though the State, over and beyond its special commission, should and could become the single and totalitarian order of human life, thus fulfilling the church’s vocation as well.” This claim is that the state had taken over the role of the church, corrupting its purpose in communicating the conscience of the people to the state.

Moral Framework for evaluating The Morality of War

The foundations of just war theory apart from Christianity finds its roots in the natural law. The natural law is “acknowledged both in the classical philosophical tradition and in the mainstream of the Christian moral-philosophical tradition, both of which generously inform the Western cultural tradition.” Natural law in the Christian tradition is informed by a perceived natural order of things and by conscience which governs the inner self. Therefore Plato’s claim that nations are always at war is true in the sense that they are always seeking a balance that is either selfish or aligns with the natural law.

The division between natural law and conscience may be connected to the relationship of the individual and the state. While the individual is governed by laws their actions are generally informed by their conscience. The state does not have a conscience but those in authority within a state do have a conscience. Their collective consciences generally ought to align with the natural law or widespread corruption. This then gives detail to the distinct roles of people and the state. The Church acts as an intermediary between the individual and the state. By being a corrective force on the collective consciences of those in authority towards natural law. It can be said that “Church and state have distinct spheres of responsibility but will best discharge those responsibilities with mutual respect and negotiated authority and influence.”

The framework for evaluating the morality of war must consider the individual and collective conscience of the people in the state. While also maintaining an awareness of the natural order. Just war theory builds on the conscience of the individuals and state by being a regulative principle between nations. Just war theory provides a standard of conduct between nations and regulates expectations. As a regulative principle it is set apart from religion in so much as the religion does not govern what parts of just war theory are enforced. Rather religion orders the ideas in the conscience of the people in the state and that in turn informs the application of just war theory.

Just war theory is divided into three parts which apply to different stages of war. Jus Ad Bellum, is latin and is about the decision to wage war, Jus In Bello about how to engage in war, while Jus Post Bellum applies to the aftermath of a war.

Jus Ad Bellum

Jus Ad Bellum is about the decision to go to war. The decision to go to war is arguably the most important aspect of just war theory. As Jus Ad Bellum is the pursuit of justice. It does not matter how well you treat your enemy during and after a war if the reason for the war is not good in the first place. The decision to go to war must be made by the proper authority, have the right goal, have a probability of success, be the last resort, proportional, and most important have a just cause.

Jus In Bello

Jus In Bello refers to justice in war. Its domain is in “how war is actually waged.” The main idea of Jus In Bello is that a distinction must be made between combatants and noncombatants. The war must be conducted in a proportional way, unnecessary violence is to be avoided. Prisoners of war must be treated well, and the weapons and tactics should not be more harsh than necessary.

Jus Post Bellum

Jus Post Bellum is the idea that after the war is over efforts must be taken to make a good and lasting peace. This is about order and justice. It may include trials about war crimes on both sides, conciliation “How can both parties imagine and move together toward a shared future?” And order ensuring domestic and international security.

How Conscience, Scripture, and Divine Justice, Affect Just War Theory

The conscience of individuals is what gives the state the ability to wage war. Therefore conscience is a limiting factor in the decision to wage war that cannot be ignored by those in power and acts as a ballast against war mongers in power. Scripture stimulates the conscience of individuals. The more that individuals in a nation understand and apply Scripture to their lives the more their conscience is affected and the morality of the state sharpened. While the knowledge of divine justice eases the harsher impulses of individuals in the state.

Conscience as a Limiting Factor in The Application of Just War Theory

Conscience is a limiting factor in war. Militaries have always had to deal with the unwillingness of soldiers to kill in battle. The conscience of individual soldiers plays a role in the moral culpability of that soldier in war. A war may be just while the actions of an individual are not, while the opposite is also true. Orders given by the state to a soldier cannot bypass the moral checkpoint of the conscience. War must be justified to the individual soldier when they kill their enemy. One soldier some fifty years after world war two said that “Even now my conscience is troubled.” Conscience is that thing which causes the individual soldier to fight or not to fight. Conscience is informed by the Holy Spirit and God’s Word.

Scripture Provides an Interface between Man and God

Scripture serves as an interface between mankind and God. Through His Word people can discern His will. As 2 Timothy 3:16 reads, “All Scripture is inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness.” This is true of war as well as Psalm 144:1 reads “Blessed be the LORD, my rock, Who trains my hands for war, And my fingers for battle.” God may train us for battle through His Word. The Bible provides us the context necessary to make right choices in morally challenging situations like war.

Divine Justice as an aspect of Just War Theory

While divine justice is the idea that God also has a part to play in war. Either to interfere or not to interfere for better or worse in the war. God has His own sense of justice and He is a God of justice. Deuteronomy 32:35 shows that God is the one who judges and gives consequence to the bad actions of others. In Romans 12:19 Paul expands on this to say that people must leave room for God’s wrath. This means taking reasonable action in war not going beyond what is necessary, Jus In Bello.

Biblical Examples of War From a Just War Perspective

Just war theory is a philosophical idea which gains its authority as an idea by being grounded in the Bible. If an aspect of just war theory is not grounded in the Bible then that aspect is not properly part of just war theory. Therefore Biblical examples of war and action highlight scenarios in which war is justified. The scenarios like those of Deuteronomy 7:1-2 where God specifically demands action call for close scrutiny as they either support or upend just war theory as it is commonly practiced.

Deuteronomy 7:1-2 and Jus Ad Bellum

Jus Ad Bellum is the idea of just war theory that says that there must be a good reason to conduct war. The example of Deuteronomy 7:1-2 upends many of the bounds of Jus Ad Bellum. In Deuteronomy 7:1-2 God sends the Israelites to a land and says “When the LORD your God brings you into the land where you are entering to possess it, and clears away many nations before you” Deuteronomy 7:1a. Then they are ordered by God to destroy the “Hittites and the Girgashites and the Amorites and the Canaanites and the Perizzites and the Hivites and the Jebusites, seven nations greater and stronger than you” Deuteronomy 7:1b. When God gives this command He orders them to “you shall utterly destroy them. You shall make no covenant with them and show no favor to them” Deuteronomy 7:2b. In this context the Israelites are a wandering people group after having left Egypt some forty years ago. While Deuteronomy 7:1-2 does not hold to many of the normal conditions of Jus Ad Bellum such as right intention, probability of success, last resort, and proportionality, it serves as the exception that sets the rule.

While just war theory might suggest in general not attacking another group solely for the acquisition of land it seems that this action is not without precedence. Regardless of any sort of just war theory this particular action was directly justified by God. Christians today generally or not so fortunate to have a direct command by God for any military action. From this story though certain conclusions about how and when war may be justified can be inferred. Such as when God calls an individual or community to action they must be ready to act even in war. Another is that when a people group is without a homeland it is not beyond reason that they might fight to control an area where they have some historical precedence. This same sort of action is seen again in the more modern example of Israel retaking the land that now makes up Israel through the Zionist Movement. And finally that humans may serve as the judgement of God, and therefore consideration must be made of the morality of both the attacker and defender. In the case of Deuteronomy 7:1-2 the tribes of Israel were the group that God used to hand out judgement on the seven tribes in Deuteronomy 9:4-5.

Matthew 22:21 and Jus Ad Bellum

In another case of jus ad bellum in the Bible Matthew 22:21 is worth considering. The Jews did not want to be in subjugation to the Romans in the first century AD. The Pharisees sought to entrap Jesus by asking if the Jews ought to pay their taxes. The way in which Jesus answered the question “Is it lawful to give a poll-tax to Caesar, or not?” Matthew 22:17b. Jesus answered “render to Caesar the things that are Caesar’s; and to God the things that are God’s” Matthew 22:21. Therefore in this context the desire to not pay taxes was not a good enough justification for war. Although other principles of jus ad bellum are factors to consider as well. Such as the fact that Israel was not powerful enough to succeed.

The American Revolution Compared to 1st Century Israel Jus Ad Bellum

The American revolution offers a comparative point with the example of Matthew 22:21. Through a comparison of these two events the principles of Jus Ad Bellum may be observed. One of the primary issues in either case was taxes which the people had no control over. It may be that in both instances there is a just cause to wage war because of the taxation. In the case of Matthew 22 there was not an authority in place to act on the people's behalf. While in colonial America there was a local government that could and did declare war. In either case there was a noble goal which is a government founded on godly values. One of the main reasons that Jesus may have cautioned the Israelites to not go to war in Matthew 22 is that of the probability of success. The Jewish people were close to the Roman empire and had no chance of defeating the Roman empire. Whereas in colonial America the chances of success were still seen as slim yet the distance to England gave America a chance. Clauswitz argued that “War therefore is an act of violence intended to compel our opponent to fulfill our will.” If we are incapable of compelling our enemy then we ought to reconsider war. A key consideration in going to war is Romans 13:1-5 which speaks to the duty of a state, the duty of the state and of the individual is to love their neighbor. Patterson suggests that “loving our foreign neighbors may mean using force to punish evildoers or right a wrong”

Conclusion

In conclusion just war theory is founded on natural law, conscience, Scripture, and bound by divine justice. A proper application of just war theory requires a clear understanding of biblical ethics. Just war theory continues to evolve and change as the way that governments and wars take place have evolved. This offers many new challenges to just war theory that are yet to be explored. Just war theory in practice is not simple or straightforward. But rather an ongoing process of the individuals in a state considering facts and consulting their conscience to find what the right action is. There will always be states and there will always be wars. So long as two people can disagree on anything there will be war. Therefore having some sort of ethical framework for when to go to war becomes necessary. As all people are governed by their conscience the state must be able to justify warfare by some means. For the foreseeable future just war theory is the best way to evaluate the decision to go to war.

Bibliography

Augustine of Hippo, “The City of God,” in St. Augustin’s City of God and Christian Doctrine, ed. Philip Schaff, trans. Marcus Dods, vol. 2, A Select Library of the Nicene and Post-Nicene Fathers of the Christian Church, First Series (Buffalo, NY: Christian Literature Company, 1887).

Barth, Karl. Ethics, ed. Dietrich Braun, trans. Geoffrey W. Bromiley (Eugene, OR: Wipf & Stock, 2013).

Barth, Karl, et al. The Theological Declaration of Barmen. Wuppertal‑Barmen: Confessing Synod of the German Evangelical Church, May 29–31, 1934. PDF accessed June 2025. Cathedral of Hope. https://cathedralofhope.org/wp-content/uploads/2019/03/The-Theological-Declaration-of-Barmen.pdf.

Belousek, Darrin W. Snyder. Atonement, Justice, and Peace: The Message of the Cross and the Mission of the Church (Grand Rapids, MI; Cambridge, U.K.: William B. Eerdmans Publishing Company, 2012), 51.

Bonhoeffer, Dietrich. Ethics. New York: Touchstone, 2024.

Charles J. Daryl, and Timothy J. Demy. War, Peace, and Christianity: Questions and Answers from a Just-War Perspective. Wheaton: Crossway, 2010

Clouse, Robert, ed. War: Four Christian Views. Downers Grove, IL: InterVarsity Press, 1991.

Grossman, Dave. On Killing: The Psychological Cost of Learning to Kill in War and Society. New York: Back Bay Books, 2009.

Holmes, Arthur F. War and Christian Ethics: Classic Readings on the Morality of War (Grand Rapids, MI: Baker Books, 1975

McQuilkin, Robertson and Paul Copan, An Introduction to Biblical Ethics: Walking in the Way of Wisdom, Third edition (IVP, 2014).

On War by Carl von Clausewitz, translated by J. J. Graham, New and revised edition, Volume 1 (London: K. Paul, Trench, Trubner, 1918).

Patterson, Eric. “Just War Theory & Terrorism.” Providence Magazine, November 2016. Accessed June 25, 2025. https://providencemag.com/2016/11/just-war-theory-terrorism/.

Previous
Previous

#176 Pastors, Laity, and Christ’s Kingdom

Next
Next

#174 The Life and Ministry of Billy Graham