Philosophical literatureBefore heaven and earth had taken form all was vague and amorphous. Therefore it was called the Great Beginning. The Great Beginning produced emptines and emptiness produced the universe... The combined essences of heaven and earth became the yin and yang, the concentrated essences of the yin and yang became the four seasons, and the scattered essences of the four seasons became the myriad creatures of the world.Huainanzi139 BC★ 3.5