If you study the works of various authors from throughout human history, you will gradually notice something peculiar that they all have in common. No matter what time period a particular work comes from, they all reflect the same level of certainty and conviction in their message.
Our ancestors did not write "Well, gee, I dunno. Maybe the Earth is at the center of the universe, but we really aren't too sure." They were absolute in their belief that the Earth was at the center of the universe and if anyone said otherwise, that person was often punished; sometimes severely.
If you think about it, the fact that our ancestors showed so much confidence in their ideas is really quite amazing. After all, they used to believe in some ideas that look pretty foolish to us today. At one time or another many of them believed that the Earth is flat; that the universe is made of only four elements; that draining blood can help heal the sick; that powered flight is impossible; etc.
How is this possible?
How could people with such a limited concept of reality be so confident in their ideas? Even more importantly, what does this tell us about our ideas today?