A basic tenet of Biblical Christianity is that man is born inherently sinful.
This is not exactly something we like to admit to. I know that I'm not perfect and I don't know anyone who is. I know some good people maybe, or people who are good for the most part -- but perfect? I don't think so. It's funny how most of us would agree that we are not perfect, but how many of us want to hear that we are sinful? We try to change the definition of what is evil, so we say we are pretty good or as good as the next person. None of us wants to think that we have the potential for evil in us.
Yet that one fact shifts our perspective on the world, history and politics. Some would say that that is a very negative or pessimistic view of life. For a Christian it is a realistic view of life. According to the Bible it explains a lot of things that have happened and are happening in this world of ours. From that realistic viewpoint, greed, lust, anger, envy, hatred, jealousy, lack of self control, all these are more understandable -- though not acceptable. Why does sin always seem to win?
In fact, from this viewpoint I am less pessimistic because I know that the evil things that happen are the way of this world. I am all the more optimistic because I know that one day all that evil will be done away with and the goodness and perfection that we so yearn for will be ours -- not pie in the sky when we die,-- but in the New Heaven and New Earth...just as we sing in "Messiah":
" Every valley shall be exalted and every mountain and hill shall be made low;
The crooked places shall be made straight, and the rough places smooth;
The glory of the Lord shall be revealed, and all flesh shall see it together;
For the mouth of the Lord has spoken." Isaiah 40:4