All you have to do is look around you to know that man has lost whatever knowledge he once had of good and evil. The world is testimony enough of this.
And it's not that we do not know what is in our good nature. Rather, it is that again and again, we are being told what it is that we do not know, what it is that seems to have somehow escaped us. Again and again, this world is content to tell us that we are naked when, perhaps, left to our own, we would never have known.
They say that things like hate and evil are learned, that they aren't inherent in who we are. They say this as they show us pictures of little children playing together, children who have no understanding that their best friend is, in the world's eyes, quantifiably different than them in some seemingly-important way. To the child, this is just a friend. And it is true also that given only to their innate hearts, people overwhelmingly reveal themselves to be those who give generously, who help selflessly, who love deeply, and who generally contribute to the overall goodness of the world. At our core, we are naked, but we know it not.
Then the world steps in.
The world steps in and tells us that there is, in fact, an "us" and a "them." That there are fundamental differences between groups of people that we cannot, and should not, ignore. The world steps in and tells us that people are taking advantage of our good natures, that we're giving more than we can afford to give, that our love is misplaced. The world steps in and shows us all of these broken things, and it sends us diving for the bushes, trying desperately to hide our newfound nakedness, though it never had been a problem before.
And isn't that the funny thing about this world? It claims to be the expert on our nakedness. It claims to have the authoritative answer to what is good and what is evil. But it spends what seems like all of its time trying to convince us only of the evil, trying to keep us from seeing the good. Trying to spin, even, what is good into that which lives only in the full light of evil. That is, "good" is living with eyes wide open to all the traps that evil has set; there is no good apart from evil.
Oh, how backward this all is! The truth is that there is no evil apart from good. Evil is nothing more than the corruption of good.
Go back to the Garden for a minute. Before Adam and Eve ate the fruit, they were naked, but not ashamed. Was their nakedness always something to be shameful of, and they simply did not know it? Of course not. That would imply that God created the world into a state of shame without telling them. That violates two fundamental characteristics of God's nature - His goodness and His truth. So it can't be that we just did not know that nakedness was bad; it truly was not bad, until evil corrupted good and told us that it was.
Before Adam and Eve ate the fruit, they lived in fellowship with the God who walked in the Garden with them. Never before had they hidden from Him. But one bite, and they are diving for the bushes. Was it evil that they had walked with God all those days before, and they only now knew what evil it was? Of course not. Once again, evil has corrupted good and convinced man of its realness.
So perhaps we have not forgotten, after all, all that we learned from that first bite of sinful fruit, all that we once knew about good and evil. Because, perhaps, this world will not let us forget. We are born knowing no better, but it doesn't take long before this world reminds us of all that we have tried so earnestly to forget. Listen to the world, and it's the Garden all over again - evil is real, good is a smokescreen, and the bush is the place to be.
Come, let us hide together.