First proposed in the book Xunzi, this term refers to fundamental principles which apply to different things. It means that by differentiating things according to their categories and by understanding these categories, a sage could acquire universal principles which apply to all things. By following universal principles, one can ensure that different categories of things can all find their proper places within a unified order. At the same time, new things can also be integrated into the existing order.

If strange things and developments which have never been heard of and never been seen before suddenly appear, they can be dealt with by applying universal principles. Xunzi

His statements are many but they are always graceful and proper, and his classification is clear. Everyday, he expounded on his views. Though he expressed his beliefs in many ways, he is always guided by universal principles that apply to all things: this is how a sage observes the world. Xunzi