本文首先說明觀心是一種反照心源的修行活動。天台宗主張一切教行皆以觀心為要，並根據《大智度論》「三智一心中得」，以及《中論》「三是偈」而成立其觀心法鬥。其次，敘述天台宗的先導人物慧文將「一心三智」發展為「一心三觀」，以及慧思主張透過禪定反見心源，實即是一種「觀心」的禪定。其後，描述智顗認為「心」即識陰，觀心即觀照虛妄識陰；湛然主張觀心即觀照陰妄心境。這種說法至宋代乃衍生出「真心觀」與「妄心觀」的諍論。再則，論述真、妄二觀之諍的起因，及其往復論辯的過程，以及智圓基於心具論的立場主張真心觀，知禮站在性具論的立場倡導妄心觀。兼及善月從「性」、「修」無礙，「解」、「行」圓融的觀點，調合了二家的諍論。結論指出天台察的觀心是一種「以心觀心」的修證方法，目的在掃除妄念和欲想，以便通向成佛之道，邁入涅槃之境。

　　　　　The paper first explains that by "observing the mind" (guan xin) is meant a religious practice involving the reflection on the source of mind. The Tiantai School teaches that observation of the mind is the foundation of all Buddhist doctrines and practices, and constitutes its own meditation method on the basis of the teaching that "The three kinds of wisdom are realized in one mind', as found in the Dazhidulun, and the "Three kinds of truth" in the Zhonglun. The Tiantai forerunner Huiwen developed the "Three kinds of wisdom in one mind" into the "Threefold meditation in one Mind", and Huisi advocated the "observation of mind" in the state of concentration. Zhiyi thought that "mind" is the consciousness skandha, and therefore taught that "observing the mind" means to penetrate the delusive nature of consciousness. Zhanran taught that "observing the mind" means to penetrate the delusive objects of the consciousness skandha. During the Song dynasty, these teachings developed into a debate about "observing the true mind" and "observing the delusive mind". The paper explains origins and developments of this debate. On the basis of the doctrine that "the mind inherently comprises all worlds", Zhiyuan advocated the