Republican liberalism
Republican liberalism is a variation of Democratic Peace Theory which claims that liberal and republican democracies will rarely go to war with each other. It argues that these governments are more peaceful than non-democracies and will avoid conflict when possible. According to Micheal Doyle, there are three main reasons for this: Democracies tend to have similar domestic political cultures, they share common morals, and their economic systems are interdependent. Liberal democracies (republics) that trade with each other, are economically dependant on one another and therefore, will always attempt to maintain diplomatic relations as to not disrupt their  economies. Liberalism, as an overarching theory, holds that diplomacy and cooperation is the most effective way to avoid war and maintain peace. This is contrasting to the theory of realism, which states that conflict will always be recurrent in the international system, whether due to human nature or the anarchic international system. Origin. The concept of Republican liberalism is thought to have initially originated from Immanuel Kant's book "" (1795). The term "Perpetual Peace" refers to the permanent establishment of peace, and was made notorious by the book. Democratic peace, commercial peace and institutional peace were all advanced in the  book as well. It takes a rather utopian view, that humanities' desire for peace will out compete humanities' desire for war. Kantian Liberalisam. Kant and the liberal school of thought view international co-operation as a more rational option for states than resorting to war. However, the neo-liberal approach concedes to the realist school of thought, that when states cooperate it is simply because it is in their best interest. Kant insisted that a world with only peace was possible, and he offered three definitive articles that would create the pathway for it. Each went on to become a  dominant strain of post–World War II liberal international relations theory. I: "The Civil Constitution of Every State should be Republican". Kant believed that every state should have Republican style form of government. As in, a state where "supreme power is held by the people and their elected representatives." Kant saw this in Ancient Rome, where they began to move away from Athenian democracy (direct democracy) and towards a representative democracy. Kant believed giving the citizens the right to vote and decide for themselves would lead to shorter wars and less wars. He also thought it was important to "check  the power of monarchs", to establish a system of checks and balances where no one person holds absolute power. Peace is always dependent on the internal character of governments. Republics, with a legislative body that will be able to hold the executive leader in check and maintain the peace. II: "The Law of Nations shall be founded on a Federation of Free States". Kant argues nations, like individuals can be tempted to harm each other at any given moment. So, rule of law should be established internationally. Without international laws and courts of judgement, then force would be the only  way to settle disputes. States ought to instead develop international organisations and rules that facilitate cooperation. In any case, some kind of federation is necessary in order to maintain peace between nations. Contemporary examples include the United Nations and the European Union, which try to maintain peace and encourage cooperation among nations. III: "The Law of World Citizenship shall be Limited to Conditions of Universal Hospitality". Kant is referring to "the right of the stranger to not to be treated as an enemy when he arrives in the land of another.". So long "stranger" is peaceful, he should not be  treated with hostility. However, this is not the right to be a "permanent visitor", simply as a temporary stay. This is applicable in the contemporary world when a country is receiving a world leader. The host country usually holds a state welcoming ceremony which strengthens diplomatic relations.