Plato also outlines grounds for restraint in battle with perhaps the earliest systematic theoretical explanation of war in his Republic. He offers ideas on creating and maintaining peace as well as argues for the necessity of moral restrictions on the fighting of war. Plato’s Republic is his consideration of the good life. Early on it becomes clear that the best life for human beings happens in cooperative communities. Since none of us are self-sufficient, good lives are based on human interdependence. Plato’s Socrates outlines a simple society where goods and services are shared to mutual advantage of all citizens, and where basic needs are met in part by forgoing luxuries. Calling this “the true city, like a healthy individual,” Socrates is pressed to consider a luxurious city, one committed to the unlimited acquisition of wealth (Socrates calls it “fevered”). It is with the city dedicated to wealth that Socrates finds the origin of war.
The society based on accumulating wealth requires a guardian class of watchdog warriors, censorship, government lies, eugenics, and the abolition of the family. And it requires war. Although scholars disagree on Plato’s own ideal society, two points on war are very clear. One, war originates in the drive for wealth, and two, war is best avoided. Additionally, if it cannot be avoided, it must be restrained. Plato’s main worry about war concerns Greeks. In Republic 470e–471b, the dialogue concerns relations among the “good and civilized” Greeks. Plato suggests that strife among Greeks will not be called war, since quarrels among Greeks will occur with the hope of reconciliation.
"Being Greeks they will not ravage Greece, they will not burn the houses, nor will they maintain that all the inhabitants of each city are their foes, men, women, and children, but only a few, those who caused the quarrel. For all these reasons, as the majority are their friends, they will not ravage the country or destroy the houses. They will carry their quarrel to the point of compelling those who caused it to be punished by those who were guiltless and the victims of it."
Although Plato does not extend such moral restraint beyond Greek enemies, he does lay the groundwork for a wider application of the immunity of innocents and the principle of proportionality, the notion that the evil of war must not go beyond the good likely to come of it. Clearly morality is relevant to war for Plato. War realism is rejected and seeds of a just war tradition are planted.
Plato also highlights anti-warism in the Crito, an early dialogue that captures the historical Socrates’ objections to war. Pacifism is not necessarily the same as anti-warism, but the critique of violence is obviously connected to the critique of war. After his trial and conviction for corrupting the youth of Athens and for teaching religion contrary to that of the city, Socrates awaited his execution. Some of his friends were convinced that they could help him escape to another city, but they had a problem: convincing Socrates that his escape would be just. Socrates argues that we should never do injustice nor should we retaliate against it. We must never do evil, and we must never return evil for evil, no matter what we may have suffered. Many scholars dismiss this as merely rhetorical, a point made only “for the sake of argument,” but Gregory Vlastos, perhaps the leading Plato scholar of the twentieth century, tells us this is an original moral insight, namely, that suffering injustice does not give one a moral justification to retaliate with violence. This undercuts virtually all justifications for violence and war throughout history. It is an especially remarkable insight for its time because punishing enemies was not only tolerated but glorified in ancient Greek culture.