Universal truth and knowledge were the goals Aristotle set for himself. Also he believed it well to keep in the good graces of the rulers. When Alexander the Great was 13 years old, Aristotle was appointed his teacher and from that time on had a deep influence on the pupil who, they tell us, came to tears because he had no more worlds to conquer. Aristotle later headed the Peripatetic or “walk about” school at Athens, so named because knowledge was imparted from teacher to student as they strolled about the groves. Aristotle wrote authoritatively on almost every subject. The sun, light, and vision, of course, received the attention of this philosopher whose word on philosophic and scientific matters was accepted by many without question as law for centuries. Even today many principles first enunciated by Aristotle are still generally respected in philosophy. In Aristotle’s book titled _Problems_ there was described the phenomenon of sunlight passing through a square hole and still casting an image of a round--not square--sun on the wall or floor. This was an astounding discovery! It may strike the reader as strange, but he may easily convince himself by making a little experiment: cut a square hole in a piece of dark paper and let the image of the sun fall on a mirror or other smooth surface and you will see that the sun is still round despite the square hole. As a word of caution, one must be careful to avoid eye strain when viewing the sun and its reflections. Several of the principal characters in motion picture pre-history ruined their eyes by studying the sun for too long a period at one time. Aristotle’s square hole and round sun experiment was a beginning and scientists were starting to learn something important about light and optical phenomena. Aristotle also made a valuable contribution to the study of vision. In his book, _On Dreams_, he noted the existence of after-images, a persistence of vision phenomenon. That faculty contributes vitally to the motion picture effect. A common example is that a whirling firebrand appears to make a complete continuous circle of fire. A strong light or image of any kind will be visible to the eye for a moment after the physical stimulus has been removed. Aristotle also was interested in color and in a study in this connection he noted that certain given plants were bleached by the sun. This was the initial scientific observation in the chain which ultimately, though indirectly, led to photography.