Rationality, Perfectibility, and Mutability premise

I have to say that I do believe in the rationality and mutability premises. Trenholm (2008) defines the premises as such: “the rationality premise – the belief that most people are capable of discovering the truth through logical analysis…the mutability premise assumes that human behavior is shaped by environmental factors and that the way to improve humans is to improve their physical and psychological circumstances” p. 353. First of all the rationality premise makes sense to me if I apply it to people; on the other hand this premise which is practiced by our government (democracy) is not always 100% correct in discovering the truth or maybe I should say a little late in discovering the truth. A great example would be our financial crisis. The example in the book regarding the mutability premise of universal education is a good one. I understand that if everyone on our planet had the opportunity to be educated it would lead to a change in not only improved human behavior but an improved planet that we live on. The perfectibility premise is one that I do not agree with. In fact it makes me think of something I would hear from a cult leader. Humans are not born in sin and that is my opinion. The statement really sent me through the roof. We are all capable of achieving goodness through effort and control but it does not mean we were born in sin. I guess I don’t consider sex to be a sin. I could just go on and on about this premise but I won’t. Maybe I interpreted the definition of perfectibility premise differently than some of you. I would really like to hear your opinion.