This paper proposed the scientific hypothesis that human beings have an “energy system” inside their body and put forward the necessity to propose the hypothesis. In details, this paper explained the hypothesis from its existence, composition, functions, and possible verifying methods. This paper argues that the human body includes both visible and invisible parts. The former is the material system and the latter is the energetic system. As matter and energy can be converted into each other, it is important to study the human body from the perspective of both the material and energetic systems, which can complement each other. The nature of the energetic system is different from that of the material system. The traditional Chinese medicine (TCM) perspective is based on energy; therefore, extending research on the human energy system may lead to the establishment of a modern TCM research field that is firmly grounded in the principles of TCM. Such a research field might generate novel findings.