In this chapter, there are presented four theories of international systems i-e liberalism, realism, radicalism and constructivism. The reading compares and contrasts the four theories and provides the scholars' stance relative to each theory. Liberalism is based on the optimism that human nature is good and stresses that evils are the product of bad institutions. Creation of a 'just society' can improve the human conditions and corrupt environment gives rise to inadequate institutions. Education is considered imperative to overcome the defects of society. States confront each other over and over again and the prisoner's dilemma provides a rationale for their 'cooperation' to avoid any greater harm.
Both liberalism and new-liberalism predict the same thing-that is cooperation but the reason of cooperation stated by both the schools of thoughts is different. Liberalism proposes the 'institutions' while neo-liberalism proposes the 'self-interest' as the motive behind cooperation. In contrary to it, realism assumes that man is flawed, egoistic, power-seeking and selfish by nature. Since states live in anarchic international systems, they remain worried of its security. There have passed many leaders who advocated realism. According to neo-realism the international structure rather than the individual states determine the course of action. Balance of power is the core principle of both the realism and neo-realism. The difference is that in neo-realism, this balance is determined by the structure of the system. In neo-realists view, a states survival is dependent upon the relative power i-e more power than other state.
Another theoretical perspective is Radicalism. According to this viewpoint, the key actors are the social classes and actions are determined by these economic classes. It believes that a radical change is required rather than slow, evolutionary or probable one. Constructivism is a relatively new school of thought in international relations. It is different from other schools of thoughts in that's it is not a uniform theory. It also sees power as important but in different sense i-e discursive terms. Individual collective identities are the key actors in Constructivism and the behavior is a state is determined and shaped by the standpoint of the elite of that state and the collective identity. It believes that process of change is an evolutionary process and it takes time to evolve.