"Finding truth is difficult and the road to it is rough. As seekers of the truth, you would be wise to withhold judgment and not simply put your trust in the writings of the ancients. You must question and critically examine those writings from every side. You must submit only to argument and experiment and not to the sayings of any person. For every human being is vulnerable to all kinds of imperfections. As seekers of the truth, we must also suspect and question our own ideas as we perform our investigations, to avoid falling into credulous or careless thinking. Take this course and truth will be revealed to you." 

- Islamic scholar Ibn Alhazen, 965 - 1040 AD