(3 of 4)
Which brings us back to Eden. Adam and Eve eat from the tree of knowledge because they have pretensions of divinity. "Your eyes will be opened," the serpent promises, "and you will be like God, knowing good and evil." Thus the original sin is often described as a kind of hubris--"the pride which sprang from [our] likeness to God," as one scholar put it. By the lights of evolutionary psychology, an essential human weakness is indeed a tendency to be seduced by our seemingly godlike rationality into thinking we can readily know good and evil; our downfall is a lack of philosophical humility, a smug assumption that our "moral" intuitions can be trusted as a guide to true morality. The effects have ranged from homicide to genocide.
Certainly, as even Williams stresses, our moral sentiments have lots of upside, including a heartening plasticity. They can be deployed less self-servingly than they were "designed" to be deployed. Darwin himself often felt pangs of concern about the plight of slaves, even though there were none in England to reciprocate his empathy. And consider the flush of compassion we feel upon witnessing, via TV, famine that is a hemisphere away. When moved by such images to donate money or canned goods--the rough opposite of greed and gluttony--we are in some Darwinian sense "misusing" our equipment of reciprocal altruism; the equipment is being "fooled" by electronic technology into (unconsciously) thinking that the victims of famine are right next door and might someday reciprocate. But that doesn't diminish the act. Our capacity to thus distort biological purpose, to prevail over our selfish heritage, is a deep source of hope and a glimmer of true goodness.
Still, to prevail comprehensively--to frustrate all or even most of the subtle selfishness built into us--takes massive, ongoing effort and painful self-knowledge. The difficulty of the exercise lends a kind of credence to what some Christians see as the upshot of their doctrine of original sin: that people are born in need of a salvation gained through repentance. To put it in secular terms: so deeply hidden from natural introspection is our badness that moral reform requires a solid jolt of enlightenment, sharp and persistent awareness of our inherent baseness.
Moral reform may or may not come as Christians prefer--in the course of accepting Jesus as savior. But certainly Jesus said some things that could lead even an agnostic toward it. He asked us to doubt the moral basis of all hatreds--even of our enemies--and to doubt our frequent feelings of moral superiority, our illusion of clarity. ("You hypocrite, first take the log out of your own eye; and then you will see clearly to take the speck out of your brother's eye.") Other religions also preach universal love and harsh self-scrutiny. Buddha said, "The fault of others is easily perceived, but that of one's self is difficult to perceive."