The “human heart” here refers to human awareness of outside attractions and desires for such attractions. It is in contrast with consciousness of moral principles, and was used in classics such as the “Old Text” version of The Book of History, and Xunzi. Confucian scholars in the Song Dynasty attached great importance to both concepts, and had interpretations and expositions about them. It was believed that the conscious mind, or heart involved two aspects. The first is the human desires for the outside world that were aroused by sensory organs such as eyes and ears, which is called renxin, or the “human heart.” The second is the consciousness of moral principles, which is called daoxin, or the “moral mind.” “Human desires” is brought about by the bodily senses and it is selfish. Therefore, the role of the consciousness of moral principles needs to be allowed full play so that excessive human desires which will lead to harm can be held in check.

The human heart is beset by danger, while the moral mind is subtle and elusive. Concentration of mind is required for sticking to the path of justice and uprightness. (The Book of History)

Consciousness and senses from the heart are ultimately the same thing. A distinction, however, may be made between the “human heart” and the “moral mind.” This is because the former refers to selfish desires brought about by the bodily senses, whereas the latter comes from heavenly principles of justice. Human desires are dangerous and lead to uncertainty. Consciousness of moral principles is elusive and rarely exhibits itself. (Zhu Xi: Preface to Annotations on The Doctrine of the Mean)