Now, you also have physicists, mathematicians, astronomers like al-Hazen, and he is credited as getting one of the more sophisticated views of how light and vision works. These are some quotes from al-Hazen. From each point of every colored body illuminated by any light, issue light and color along every straight line that can be drawn from that point. This is a fairly sophisticated view of how light actually works. And he's also credited with using and understanding the scientific method several hundred years before the Renaissance in Europe. The duty of a man, the duty of the man who investigates the writing of scientists, if learning the truth is his goal, is to make himself an enemy of all that he reads and attack it from every side. He should also suspect himself as he performs his critical examination of it so that he may avoid falling into either prejudice or leniency.