A new theory to explain geometrical illusions produced by crossing lines

Due to the diffraction of light and other optical distortions of the eye, the image of an object is not exactly the same as the object. When two objects are close enough, their two images overlap so as to form one image, located at a position somewhere between the two original images. This fact is used to explain illusions produced by the crossing of lines, including Poggendorffs, Zollner’s, Hering’s, Wundt’s, the Müller-Lyer and other illusions of this class.