顧憲成、高攀龍是東林書院的重建者與晚明實學思潮的倡導者。他們不但是理學家同時也注重五經，尤長於《易》，他們針對王學末流高唱「無善無惡」心之體以致狂禪派以空理空性來曲解陽明「四句教」中這第一句話甚感不妥。於是，他們重振儒學性善論的傳統，且賦予天道的形上根源。他們回到周濂溪、張載、程伊川和朱熹重視易學道德形上學的傳統，將人性之善與天道繼善成性的生生之善德善理通貫為一本論。他們也針對晚明幾近狂禪派的學者將「四句教」第一句視為本體而與被視為工夫的後三句割裂感到不滿。顧、高二人不但借助朱熹居敬窮理的工夫論以救正王學末流工夫路數的空洞化，且重申本體與工夫不二，「講」與「習」不可分，內聖的「立本」與人文化成天下的「致用」應緊密結合的實學，這是他們開展《易》書經解學的詮釋立場和思路脈絡所在。本文由四個面向來探討此二人易學中的天否合德論，（一）顧、高易學的時代課題及理論取向；（二）以一陰一陽之道言生生不息的天德；（三）工人合德的價值抉擇與實踐工夫。文末則予一簡要的評論。

　　　　　Gu Xian-cheng and Gao Pan-long were the re-founders of the Dong Ling Academy and the advocates of concrete thinking in the late Ming Dynasty. They specialized in not only Neo-Confucianism but also the Five Books, especially the Book of Yi. They couldn't agree with the mediocre followers of Wang yang-ming's doctrine, who distorted the first sentence of Wang's four-sentence teachings; therefore, Gu and Gao re-established the tradition of the good-nature theory and possessed the way of Heaven with metaphysical sources. They returned to the tradition of Zhou Lian-xi, Zhang Zai, Cheng Yi-chuan and Zhu Xi, emphasizing on the moral metaphysics of the doctrine of Yi and organizing the everlasting good virtues and principles about the "good nature" and "way of heaven succeeding goodness into nature" into a coherent ontology. They also disagreed with the almost wild zenist scholars of the late Ming Dynasty who broke apart the four-sentence teachings, seeing the first sentence as the entity and the latter three as the cultivation. Gu and Gao borrowed Zhu Xi's theory about "being respectful to exhaust the principles of things" to remedy the hollowness of the approach of those mediocre followers of Wang and re-insisted on the concrete thinking of the unity between entity and cultivation, teaching and learning, and entity-building and employment. This is how they set out to interpret and make sense of Zhou Yi. In this paper, we are to discuss Gu and Gao's theory about the unity of the virtue of Heaven and Man in their doctrine of Yi through the following four aspects: first, the current issues and theoretical orientations about Gu and Gao's doctrine of Yi; second, explaining the everlasting virtue of Heaven in terms of Ying/Yang; third, discussing the virtue of heaven given to Man regarding the way of Heaven; and fourth, the value choices and practical cultivation of the unity of the virtue of Heaven and Man.