On the Marvelous Occurrences in the World

if a man is moved vigorously in a circle, all things will seem to move circularly. A thing is also judged to be of another color because of the quality of the medium: just as through red glass, all things appear red. But also from the diverse reception of light, different colors are judged: as can be seen in the neck of a dove, and on silk cloth. A staff existing in water appears broken, because it is seen through a refracted ray. A seen object is judged to be in a different position if it is seen through a reflected line: this is clear when we judge an object seen through the reflection of a mirror to be at the bottom of the mirror, but it is also then judged to be smaller than it is. An object moved very quickly is judged to be resting because of distance: this is clear in the Sun and the stars, which seem to us to be at rest, unless after exact consideration; it is also clear in a person coming from afar in a straight line. Thus, due to an unnatural disposition of the organ, for example, if there is red or yellow humor in the eye, all things are judged to be yellow or red; if there is thick humor in the middle of the pupil, all things appear perforated; if there is black humor, all things seem full of flies. Furthermore, error occurs because of the brevity of time in judgment: just as when a burning brand is moved quickly, it is judged to be a line of fire, or a circle of fire; for time is required for judgment, and the more distinctly and particularly a thing is discerned, the longer time is needed. Hence, if a thing passes before the eyes suddenly, it