The concepts of good and evil are easiest to explain or define if one believes in (or even just assumes for the sake of having moral moorings) a single, omniscient, omnipotent creator (God). Good is that which is like God, evil is that which is contrary to God or good. The notion of an omniscient, omnipotent god who is evil is absurd; but that's a rather involved polemic. Assuming men are created in the image of God, but that somewhere along the line we departed from Him (or Her, if you insist), it is apparent that all of us are comprised of both good and evil.

i think good and evil is like us left hand and right hand,the infant's hands are both smart. but as time goes,one hand will more smart,and the other became dumb.the good and evil is the same,when one is spring up,the other will slow down,but both are existed.