The concept of junzi is the central issue in the Zhongyong, one of the most important Confucian books. A junzi leads a life starting with the original disposition of cheng 诚 (being truthful to the real self). This paper analyzes the disposition of cheng to reveal two kinds of good in human existence, that is, the natural good, which is present in cheng; and the idea of good, which is a conceptualization of the natural good. The natural good is actually equal to the nature endowed by the Tian, and so it is primary and absolute. Meanwhile, the idea of good is secondary and can be improved by self-cultivation. The distinction and interaction between these two kinds of good are crucial in conceiving the concept of junzi. Yet, the distinction is so subtle that it often confuses people in self-cultivation. In fact, people in their actual lives may mix them up and perceive only the idea of good. We call this the junzi impasse. The Zhongyong does not offer enough discussion about this impasse. Since this confusion may cause the termination of self-cultivation, this paper offers a comparative discussion in the light of Christian guilty consciousness, and attempts to propose a solution to the junzi impasse.