The meaning of delusion imply either clinical significance or psychic intentionality in our ordinary life experience, it is a very common word used as a noun, adjective, or verb. It has been a long time from the start to define the symptom, yet the controversy about the definition does not end till nowadays. The current definition in DSM-Ⅳ was depreciated for its compromise of pragmatism and convenience, lack of clarity of epistemology, and need to be examined and redefined. The article reviewed and commented on the early-modern major hypothesis of psychiatry and psychology about delusion, and reflected on the deeper dimension of the symptom with a stance on human life experience. What was discussed include religious belief, literary works, and philosophical propositions, all related to humanistic concerns. The commentary involved the definers' hypothesis and attitudes to the phenomena, and consequential treatment approach, and aids medician in encountering the very unique psychic phenomena with a holistic view.