論文嘗試從天台圓教「一念心」即「一念無明法性心」之思想，且「一念三千」即「一念無明法性心即具三千」之架構，說明由「無明即法性，法性即無明」之「法性」與「無明」詭譎相即，所帶顯出之「兩重存有論」——即「法性無住，法性即無明」之「執的存有論」與「無明無住，無明即法性」之「無執的存有論」。並探究此兩重存有論對天台圓教於淨土權實之特殊義涵，從而於「穢土」（人間）與「淨土」之關係有所說明。 This paper attempt from the Perfection Doctrine of Tian-tai School to discuss "the heart of one single mind" as well as "The Heart of One Single Mind Embracing Ignorance and Dharma-nature Simultaneously", and the construction of the "one mind containing three thousand worlds" as well as "The Heart of One Single Mind Embracing Ignorance and Dharma-nature Simultaneously as three thousand worlds exist where mind exists" explain the "ignorance" namely "dharma nature", which from "the heart of one single mind embracing ignorance and dharma-nature simultaneously" that reveals the structure of the "two-ply ontology"——the "inflexible ontology" and the "non-inflexible ontology". Furthermore, this paper will research into the implication of the "two-ply ontology" which the expedience-reality of the pure land in the Perfection Doctrine of Tian-tai School, and so as to expound the relation between the “contaminated-land”（the world） and the “pure-land”.
