 While Kihwa’s noble effort and his elegant solutions were praiseworthy, it was not meant to buck the decisive trend of the age and it was too isolated to contain the massive wave of Neo-Confucianism, which was the leading Zeitgeist at the time. Succeeding Chŏng, who perished untimely due to a political conflict, Kwŏn Kŭn 權近 (1352–1409) and others such as Yi Onjŏk 李彦迪 (1491–1553) seamlessly propelled Neo-Confucianism to the status of philosophical orthodoxy. While not fully prepared to be explosive in its creativity and imagination, this phase of Korean Confucianism clearly ushered in a new era of appropriation that nicely prepared the next phase of full development. Among others, Kwŏn was the one of the earliest who systematically developed the metaphysics of Principle and Vital Force, suggesting that the heart/mind in us must have its own nature, which is none other than the heavenly principle (chŏnli 天理). In other words, the heart/mind is Principle in terms of its Essence, but, in respect of Function, because it is mixed with Vital Force, issues feelings (chŏng 情) or intentions (ŭi 意). Unbeknownst to him, Kwŏn served as the catalyst for what is known as the “Four-Seven Debate (see below)” (Kim 2016b). But it is in the middle of the sixteenth century that Korean Neo-Confucians were ready to go beyond the stage of mere appropriation and began making rich, dynamic and lively contributions to the in-depth understanding of the central Neo-Confucian ideas. They even brought about new themes not prevalent in the original form of Neo-Confucianism. It is well-known that, with the “Four-Seven Debate”, which originated in the mid-sixteenth century, the Korean Neo-Confucians made a remarkably lively and impressive contribution to the importance of emotions in our examined life. The debate originally took place between T’oegye and Ki Taesŭng (1527–1572 pen name: Kobong) when they began exchanging letters in the spring of 1559. As “the most important intellectual event in the entire history of Korean Confucian thought” (Kalton et al. 1994), the debate was prima facie over the origin of Four Sprouts and Seven Emotions (such as joy, anger, love, fear, sorrow, hatred, desire). But when you examine it carefully, you can see that it is about (1) the feasibility of a metaphysics of Principle (i) and Vital Force (ki) in terms of their causal efficacy and normativity and (2) its moral and psychological philosophy of mind, human nature, and feelings, and, most importantly, (3) how best to achieve sagehood despite our emotions in our examined life with bodies.