This resulted in a battle of structuralism versus functionalism. The conflict theory attempts to bring together structural functionalism and Marxism. His externalist epistemology, called "proper functionalism", is a form of epistemological reliabilism. His theoretical approach blended together Marxism, diffusionism, and functionalism. The major perspectives historically have been Marxism and structural functionalism. Some call the school of thought rational functionalism instead of liberal institutionalism. Corporatism is related to the sociological concept of structural functionalism. Rationalism of design was dismissed but the functionalism of the building was still somewhat intact. The 1960s and 1970s saw the evolution of modernist architecture and functionalism. Plantinga discusses his view of Reformed epistemology and proper functionalism in a three-volume series. He identified three main limitations&colon; functional unity, universal functionalism and indispensability. A major issue in contemporary Holocaust studies is the question of "functionalism" versus "intentionalism". However, both structural functionalism and the conflict theory have received major criticisms. It also marked a major contribution to the theoretical concept of structural functionalism. Comte's emphasis on the interconnectedness of social elements was a forerunner of modern functionalism.