International relations theories can be divided into "positivist/rationalist" theories which focus on a principally state-level analysis, and "post-positivist/reflectivist" ones which incorporate expanded meanings of security, ranging from class, to gender, to postcolonial security. Many often conflicting ways of thinking exist in IR theory, including constructivism, institutionalism, Marxism, neo-Gramscianism, and others. However, two positivist schools of thought are most prevalent: realism and liberalism; though increasingly, constructivism is becoming mainstream and postpositivist theories are increasingly popular, particularly outside the United States.