When, at the beginning of summer, thunder--electrical energy--comes rushing forth from the earth again, and the first thunderstorm refreshes nature, a prolonged state of tension is resolved. Joy and relief make themselves felt. So too, music has power to ease tension within the heart and to loosen the grip of obscure emotions. The enthusiasm of the heart expresses itself involuntarily in a burst of song, in dance and rhythmic movement of the body. From immemorial times the inspiring effect of the invisible sound that moves all hearts, and draws them together, has mystified mankind. Rulers have made use of this natural taste for music; they elevated and regulated it. Music was looked upon as something serious and holy, designed to purify the feelings of men. It fell to music to glorify the virtues of heroes and thus to construct a bridge to the world of the unseen. In the temple men drew near to God with music and pantomimes (out of this later the theater developed). Religious feeling for the Creator of the world was united with the most sacred of human feelings, that of reverence for the ancestors. The ancestors were invited to these divine services as guests of the Ruler of Heaven and as representatives of humanity in the higher regions. This uniting of the human past with the Divinity in solemn moments of religious inspiration established the bond between God and man. The ruler who revered the Divinity in revering his ancestors became thereby the Son of Heaven, in whom the heavenly and the earthly world met in mystical contact. These ideas are the final summation of Chinese culture. Confucius has said of the great sacrifice at which these rites were performed: "He who could wholly comprehend this sacrifice could rule the world as though it were spinning on his hand."