정철
However, the dispute on whether Jeong should die or not was the sole, or even the most influential, cause of the split. The students of Jo Sik had suffered terrible damages by Jeong Yeorip's purge, while the followers of Yi Hwang had not lost anyone. Moreover, Yu Seongryong, the most influential of Yi Hwang's students, retained a close relationship with Jeong Cheol, who led the purge. Thus, Jo sik's students wanted to kill Jeong Cheol more than Yu Seongryong and other students of Yi Hwang did. Another cause for division was that Jeong Inhong, the most favored student of Jo Sik, had a contempt for Yi Hwang and his pupils, who formed a large part of the Easterners. These differences within the Easterner camp led to the followers of Yi Hwang becoming largely Southerners, while the followers of Jo Sik became largely Northerners.