Mo Jing, also known as Mobian, mainly discusses epistemology, logic and natural science. Mo Jing consists of four chapters: classic, classic, classic and classic (including six chapters of Daqu and Xiaoqu). Jing Shuo is an explanation or supplement to Jing Shuo. Others think that the classics were written by Mo Zhai, the founder of Mohism, and recorded by his disciples.

Logic accounts for the largest proportion in Mo Jing's content, followed by natural science, including geometry 10 and about 20 physics, mainly including mechanics and geometric optics. In addition, there are psychological, political, legal, economic and architectural regulations.

Four basic laws of geometric optics;

1. Law of straight-line propagation of light: In an isotropic homogeneous medium, light propagates along a straight line.

2. Law of independent propagation of light: When light from different light sources passes through a certain point from different directions, they do not affect each other.

3. The law of light reflection: When a beam of light is projected on the surface of a smooth medium, a part of the saved light is reflected back to the original medium, which is called reflected light.

4. The law of refraction of light: When a beam of light is projected on the smooth surface of a medium, in addition to some light being reflected, some light is incident into the second transmission medium through the interface of the medium, which is called refracted light. Refracted light and incident light are located on both sides of the normal respectively, and are in the same plane with the normal.