The Importance of Optimism

I can recognise that there is a lot of evil in the world. People are suffering now as we speak. But just to take a minor example, dentistry has improved dramatically in the last century. Human capacities for self-government haven't improved very dramatically. The propensity of human beings to commit genocide on their neighbours hasn't changed a bit. It's not clear to me that we've improved at all since the days of Joshua and Judges where in the Bible the people imagined that God is telling them to kill off all the neighbours so they can have their land. I think optimism and idealism tend to be deeply rooted in individuals' personalities and so it's not something that they can just easily