The most difficult form of bias to divorce yourself from is that unthinking tendency to make assumptions about other people based on your own subjective experience - a bias of perspective. We do this with people who are living among us, and in these cases one might not be so wide of the mark since we tend to share our lives with people of the same culture, education system, and history. But, when we try to understand the actions and beliefs of people who lived in the distant past we will fail miserably if we pay no mind to the gulf that divides us: the very way we think - our habits of thought - would be foreign to an Egyptian peasant living 5000 years ago, "before philosophy".
That is the name of a book I bought for mere quarters at Afterwords, a second-hand bookstore located downtown St. John's, and I do believe I will write a book report of sorts on it (oh my, if my younger self could see me willingly using my free time to write book reports....) It is, as you can see from the subtitle, "a study of the primitive myths, beliefs, and speculations of Egypt and Mesopotamia".