Reductionism is a major methodological mistake in research and generally in thought; because it can pose as an obstacle to comprehensive views about the researched issue. This issue is more tangible in religious phenomena - due to the multidimensional entity of this subject – and can be more destructive. A researcher through focusing on one role and aspect of religion and concentrating on a theoretical frame work gives direction to religious studies. Dogmatic thought, modernism approach, pluralism, the pluralism and relativism of post modernism all in their own unique ways can lead to the development of reductionism in religious phenomena. Contemplation in the researcher's background of thought, motives, and his expertise regarding the categorization of religious phenomena, can help us exclude exclusivism and unilateralism in religious studies and direct us towards hidden aspects of reductionism approaches in relation to religious issues. Meta-post modernism is after introducing comprehensive view points, which pluralism reflects truth within them. This article through analyzing related ideas and approaches, which have led to these theories, introduces reductionism and unilateralism in religious phenomena.