本文擬以周濂溪「誠」概念為核心，探討其對於〈中庸〉、《易傳》思想之融通。〈中庸〉「天命之謂性，率性之謂道，修道之謂教」，將孔門不可得而聞之「性」與「天道」問題提點出來，又以「誠」言天道性命之相貫通，就天道言人道，而立「誠者，天之道；誠之者，人之道。」之論；《易傳》則在宇宙觀及天道論有精闢之論，以「一陰一陽之謂道」言天道，而有「繼善成性」之性命觀；就儒家「天道」、「性命」之學說言，二者之論實相為表裏，在宋明時期成為理學家天道性命之學的主要依據。本文首先就「誠」之字義及觀念內涵之發展敘述之；其次則論述〈中庸〉及《易傳》天道性命論之要旨；再從濂溪之「天道論」論「誠」為性命根源，及就其「修養論」論「誠」為工夫及境界，以闡論濂溪「誠者，聖人之本」、「聖，誠而已矣」之理論，並明其所承繼及融通之〈中庸〉、《易傳》思想。

This article is meant to revolve around Zhou Lien-xi’s idea of “genuineness” and inquire his understanding about the thought of Yi Zhuan, “The Doctrine of the Mean”. “The Doctrine of the Mean” points out the questions of “nature” and the “heavenly way” and address the correspondence between the heavenly way and human nature by means of “genuineness.” Yi Zhuan makes some brilliant statement about the cosmos view and the heavenly way. These two statements, complementary to one another, became the foundation of Neo-Confucians’ doctrine of the heavenly way and human nature. This paper proceeds along the evolution of the literal meaning and immanence of “genuineness,” then Zhou’s theory of “genuineness,” and finally the thought in Yi Zhuan, “The Doctrine of the Mean” as he inherited and understood.