Born near the town of Kang-Nung in Kwangwon-Do province, Yi I (Yul-Gok) was fortunate to have a very talented and artistic mother, Sin Saim-Dang. She was unusually accomplished for a woman of those times and was known as an excellent painter. Well-respected throughout Chulla and Kyongsang provinces during her lifetime, she has become more renowned throughout the world in the last 300 years. It is most likely that her talent had a profound effect on her son's upbringing, he is said to have been able to write characters as soon as he could speak and to have composed an essay at the age of seven.
At the age of 29, Yi I passed a higher civil service examination with the highest marks, and his government service started in that year. The thesis written by Yi I was a literary masterpiece interwoven with erudite knowledge of history and Confucian philosophy of politics, also reflecting his profound knowledge of Taoism. At age 34, Yi I authored an eleven-article treatise devoted to clarifying his conviction that righteous government could be realized even in his days, showing his aspirations for it and also measures to achieve it.
His mother's death, when he was 36 years old, brought him deep sorrow. Being close to his mother, Yi I was very distressed when she died in 1559. According to some sources, as a result of this grief he temporarily renounced the world and took refuge in a Zen Buddhist monastery in the rugged and beautiful Diamond Mountains. During his one-year stay there, he meditated, reflected on Buddhist philosophy, and became well versed in Buddhist teachings. He may have thought after three years of lamentation that the Buddhist phrase, "life is transient," would ease his sorrow. He may have understood that the Confucian teaching, "Preserve your mind and nurture your nature," was synonymous with the Buddhist teaching, "Open your mind and see your nature." Finally, he may have regarded it as a pleasure simply to rest in the countryside. After leaving this monastery, he returned to society and devoted his life to studying Confucianism. In later years, as he developed into a renowned philosopher, he acquired the pseudonym Yul-Gok.