Ignorance, the root and stem of all evil. -Plato
Plato there completely grasped it. There's no evil or darkness in the sense people tend to think about it. Just like darkness is the absence of light - evil is the lack of awareness. You don't fight darkness with light; you just bring light into darkness. Therefore, you make it aware.
And good or light consists of awareness, love, truth, justice, beauty, innocence, understanding etc. Darkness or evil is the absence of all these archetype values. This Universe purposefully consists of good and evil and your free will is the access to each of this. In other words, you get to choose. And you become what you choose, so choose carefully my friends.
"It takes considerable knowledge just to realize the extent of your own ignorance."
Thomas Sowell