The purpose of this paper is to explain why Yi-Hwang(李滉) had suddenly asserted the ‘Lizado theory’(理自到說) after modifying his early theories just 20 days before his death. To find the answer to these questions, We attempts the following. First, it is necessary to examine Yi-Hwang s early ‘theory of investing things’(格物論). In Yi-Hwang s early ‘theory of investing things’, he succeeded Chu-Hsi(朱熹) s ‘theory of investing things’. At that time, Yi-Hwang completely separated the Li that is the object of recognition from the mind that is the subject of recognition. And He admitted only the active nature of the mind that is the subject of recognition, and not the active nature of the Li that is the object of recognition.\nNext, we examine how Yi Hwang s early ‘theory of investing things’ was modified into the later ‘theory of investing things’, and why such modifications were made so late. Based on Chu-Hsi s term ‘Lipilyouyong’(理必有用), Yi Hwang declares that there is an active nature in the object of recognition.\nFinally, we examine what led Yi Hwang to claim the ‘Lizado theory’, which is interpreted as expressing the active nature of the Li just 20 days before his death. The reason why Yi Hwang claimed the ‘Lizado theory’ is because Chu-Hsi s the theory has the following problems. That is, If subject and object are completely separated during recognition process, it is impossible to communicate between them. Also If Li cannot play his part as a moral law in the foster process, there are weaknesses in turning an individual into a moral being.