This involves philosophy. Many things in the world are contradictory, but they are often universally related. For example, predators and prey are inherently antagonistic, but if there are no predators, they will be killed by Russia. If there are no predators, they will over-breed, affect the ecological balance and eventually perish. Therefore, they are interdependent. Everything in the world is the inevitable product of nature and human development, so the heart, spleen, lung and kidney belong to the five internal organs.