His father was a Fourth State Councillor (좌찬성; jwachanseong) Yi Won-su, and his mother, Shin Saimdang, was an accomplished artist and calligrapher.

He passed special exams with top honors with a winning thesis titled Cheondochaek (천도책; 天道策; lit.

[3] He served in various positions in government from the age of 29, and visited the Ming dynasty as seojanggwan (서장관; 書狀官; lit.

He also participated in the writing of the Myeongjong Annals and at 34, authored Dongho Mundap, an eleven-article political memorial devoted to clarifying his conviction that a righteous government could be achieved.

His many documents and theses were presented to the royal court but when political conflicts escalated in 1576, his efforts proved fruitless and he returned home.

[3] According to legend, he had a pavilion built near the ford of the Imjin River in his lifetime and instructed his heirs to set it ablaze when the king had to flee northward from Seoul, to provide a guiding beacon.

His school of Neo-Confucianism placed emphasis on the more concrete, material elements; rather than inner spiritual perception, this practical and pragmatic approach valued external experience and learning.

[5] These are some of Yi's published writings:[10] Yulgongno, a street in central Seoul, is named after him,[16] and he is depicted on the South Korean 5,000 won note.