 Post-positivist epistemology rejects the idea that the social world can be studied in an objective and value-free way.It rejects the central ideas of neo-realism/liberalism, such as rational choice theory, on the grounds that the scientific method cannot be applied to the social world and that a "science" of IR is impossible.A key difference between the two positions is that while positivist theories, such as neo-realism, offer causal explanations (such as why and how power is exercised), post-positivist theories focus instead on constitutive questions, for instance what is meant by "power"; what makes it up, how it is experienced and how it is reproduced.