It is impossible for finite, material systems to perform flawlessly all the time. However, most of the time, human beings do quite well. Human nature is inherently evil and, along with the rest of the natural world, in need of radical reform. There is an enormous gap between how things actually work and the ideal, which is based on some transcendent standard. It's up to the enlightened few to change things, in light of their vision of the good.
Humans have no fixed or determinate nature.
We are free to make of ourselves whatever we will. Evil is an unavoidable by-product of this radical freedom. Human nature as created is wholly good. At some specific point in the past, the ancestors of humanity misused their freedom, producing an inherited, congenital flaw in all of their descendants. The fall of Adam and Eve is a representation of a universal phenomenon.