For example, man is composed of mind, which is sung-sang, and body, which is hyung-sang. The invisible mind is the subject and exercises control over the visible body, which is the object. Likewise, the other created beings, though differing in value according to their level of existence, all have an invisible sung-sang character, which is the cause controlling the body, which is hyung-sang. For example the instinct of animals, the instinct of plants and the inherent directive nature of inorganic matter all function to cause and control their bodies or external forms to maintain their existence. Thus, we can readily understand that all things exist through the more fundamental reciprocal relationships of sung-sang (mind) and hyung-sang (body).