Chuang-tzu - In the world is the continuation of Book of Chuang Tzu. It was the learning case for people in later Zhou Dynasty (in the past it is called Learning Case TodayAcademic History ) If you do not read Chuang-tzu - In the world, you will not understand the real intention of Book of Chuang Tzu nor the overview of academy in the later Zhou Dynasty. Therefore, any Chinese scholars today will attach great importance to Chuang-tzu - In the world, regarding it as the priority.