Plato is the first philosopher who speaks about the genesis of dialectic between civil war and outside war. The war among States may be considered a righteous war when an outside enemy threats the freedom of the polis, as freedom – from Plato’s point of view and the whole classical Greek culture point of view – is the fundamental human right that makes a man a citizen and not a slave. From Plato’s point of view this objective can be achieved by means of the education promoted by the State that helps the citizens to realize his essence as man. The State, therefore, realizes the natural order among citizens thus educated, that may only consist in a proportional equality of all citizens for their friendship and thus for peace. The polis becomes a unity and a real political community only thanks to the peace granted by that friendship.