The object of this article is YangChon 陽村 GueonGeun 權近 who is a representative scholar of Neo-Confucianism in the early years of the Joseon Dynasty and also can be called the founder of whole Joseon Neo-Confucianism at the same time. In this paper, I try to explain Tianrenheyi 天人合一 as his belief and aim can be understood and reached through theoretical basis of Tianming 天命 and Xingli 性理, Jing 敬 as a specific practice of mind cultivation. I shall first review the fundamental notions of Ruxuetushuo《入學圖說》which is Gueoneview the fundamental notions of through theoreticalure of it. From this, I shall identify theory of Gueon serving as foundation of Xinxue 心學 which is the point of Neo-Confucianism in the Joseon Dynasty.