Āyatana is one of the core terms of early Buddhism, yet academic research regarding this important topic is lacking. The conflicting interpretations of āyatana lies in the question of whether or not it contains unconditioned (asaṅkhata) phenomena. This paper summarizes the research results based on the early Buddhist literature and draws the following conclusions following a comprehensive discussion: (1) The twelve āyatana-s are conditioned phenomena, distinct from unconditioned phenomena. Therefore, the twelve āyatana-s should not be regarded as asaṅkhata. (2) The application of āyatana has both theoretical and practical significance: from the theoretical point of view, it clarifies the scope of early Buddhism, it establishes the ideological foundation centered on sentience, it constructs the theoretical basis of Buddhist epistemology, and establishes the theoretical framework for the Buddhist notion of the Middle Way. From the perspective of practice, the object and content of introspection (vipaśyanā) are clearly defined; it is the guide in the practice aimed at liberation. This preliminary discussion of the term shows that, based on the teaching of the early Buddhist literature, the twelve āyatana-s do not include asaṅkhata phenomena.
