天台宗=Tiantai School; 智顗=Zhiyi; 一佛乘止觀思想=The Theory of Meditation of One Buddha Vehicle; 界=Realms; 救度學=The Theory of Deliverance; 修道論=The Theory and Method of Practice
Since Zhiyi talked about the‘Three Great Works of Tiantai’, his works overflows with the idea of‘One Buddha Vehicle’from“Lotus Sutra”; These include the expound of the theory to explain the idea of ‘One Buddha Vehicle’ simultaneously includes the method of meditative ‘śamatha-vipaśyanā’ to explain the idea of ‘One Buddha Vehicle’. Although, in the section of meditative‘śamatha-vipaśyanā’which is regarding the idea of‘One Buddha Vehicle’does not like what he was expounding the theory of the idea of‘One Buddha Vehicle’, it is still highly valued by the scholars in the past and present; However, this should be the beginning of the idea of meditative‘śamatha-vipaśyanā’ by Zhiyi, we could not find any research works specifically discussing this particular topic.
In the idea of‘One Buddha Vehicle’by Zhiyi, its purpose is to use meditative‘śamatha-vipaśyanā’ to amalgamate Śravakayana, Pratyekabuddhas and Bodhisattva the three vehicles of Buddhism into‘One Buddha Vehicle’; Or to lead and integrate the three other teaching namely, Tripitaka Teaching, Common Teaching and Distinct Teaching into the Perfect teaching. Nevertheless, in order to resolve the issues of varies Separations of Realms existed in the above Four Vehicles or Teachings, one has to find the actual solution from deliverance, theories and methods of practices within the idea of ‘One Buddha Vehicle’ established by Zhiyi.
Regarding the issue of deliverance of Śravakayana, Pratyekabuddhas and Bodhisattva of Tripitaka Teaching, Zhiyi provided solutions based on the discourse of the idea of 'One Buddha Vehicle'. As for the theory of deliverance within the meditative‘śamatha-vipaśyanā’ of the idea of 'One Buddha Vehicle', Zhiyi provided two main methods of Deliverance: to deliver the practitioners of Common Teaching to the Distinct Teaching and ultimately to the Perfect Teaching , in order to resolve the issue of Separations inside and outside of the Three Realms encountered by them, to deliver the practitioners of Common Teaching and Distinct Teaching to the Perfect Teaching, in order to resolve the issue of Separation within the Three Truth leaned towards the Perfect teaching encounter by them, hence becomes ‘One Buddha Vehicle’. The theory of practice within the idea of meditative‘śamatha-vipaśyanā’in‘One Buddha Vehicle’can be divided into the theory and method of‘Expedient Calming and Contemplation’and the theory and method of‘Manifestation Ultimate Truth’. The theory and method of ‘Expedient Calming and Contemplation’is to base on the structure of deliverance meditative‘śamatha-vipaśyanā’in the idea of‘One Buddha Vehicle’and according to the faculties of the Tripitaka teaching, Common teaching and Distinct teaching to gradually integrate the Three Teachings practitioners into the Perfect teaching of ‘One Buddha Vehicle’. Whereas, the theory and method of ‘Manifestation Ultimate Truth’ is for the Perfect Teaching practitioners to use the “Threefold Contemplations of One Mind’ the meditative ‘śamatha-vipaśyanā’ process to extinct the defilement in order to achieve the ultimate wisdom.