Listing's law is a principle that governs the coordination of eye movements. It states that the eye rotates about a fixed axis during gaze shifts. There are several synonyms used to refer to Listing's law, including Helmholtz's law of equal innervation, Donders' law, and Hering's law of the quality of the activity. The Helmholtz's law states that muscle tension is proportional to the angle of eye rotation and is responsible for ensuring that the eyes rotate the same amount during conjugate eye movements. Donders' law refers to the fact that the eye cannot move in two directions at once and must follow an angular trajectory. Hering's law states that the position and direction of the eyes are determined by the activity of the extraocular muscles. All of these laws are used to describe the eye's movements during gaze shifts, and are important for understanding how the visual system works.