Despite all his difficulties, he became a student of Yi Che-hyŏn and along with other leading thinkers of the time, such as Chŏng Mong-ju, his penetrating intelligence started to affect the Korean politics.

Deciding all policies from military affairs, diplomacy, and down to education, he laid down Joseon's political system and tax laws, replaced Buddhism with Confucianism as national religion, moved the capital from Kaesong to Hanyang (present-day Seoul), changed the kingdom's political system from feudalism to highly centralized bureaucracy, and wrote a code of laws that eventually became Joseon's constitution.

After the sudden death of Queen Sindeok in 1398, while King Taejo was still in mourning for her (his second wife and mother of Yi Bang-sŏk), Yi Pang-wŏn struck first by raiding the palace and killed Chŏng Tojŏn and his supporters as well as Queen Sindeok's two sons including the crown prince, in a coup that came to be known as the First Strife of the Princes.

Such thinking of Chŏng is detailed in his book Joseon Gyeonggukjeon (Korean: 조선경국전; Hanja: 朝鮮經國典), on which the official state legal code, Gyeongguk daejeon, is based.

However, Yi Pang-wŏn, who had passed the civil service examination of Goryeo, would have understood the implications of Chŏng's thinking.

Shortly after Joseon's founding, Chŏng and other prominent scholar-officials set out to identify the trappings of Goryeo that precipitated its demise and put forth reform ideas.

Chŏng argued that land should be returned to the central government (and distributed to small farmers) and that private armies should be abolished, including those of the princes.

It is also argued that Yi Pang-wŏn could not have afforded to allow Chŏng the time to compose a poem in the midst of a full-blown coup.

Using Cheng-Zhu school's Neo-Confucian philosophy as the basis of his anti-Buddhist polemic, he criticized Buddhism in a number of treatises as being corrupt in its practices, and nihilistic and antinomian in its doctrines.

Anyone outside this system, including Buddhist monks, shamans, and entertainers, he considered a "vicious" threat to the social fabric.

For example, Song Si-yŏl, the most reputable philosopher of the 15th century Joseon dynasty, always included a word "insidious" when he mentioned about Chŏng Tojŏn.

[2] Yi Ik, also a renowned Korean philosopher of the Middle Age of the dynasty, referred to him as "a figure who deserved to be killed" in his book, Seong Ho Sa Seol.

Chŏngjo, 22nd King of Joseon, republished Sambong Jip, recognizing his work building the political systems and intellectual foundations of the dynasty.