There are those Christians - me being one of them - who believe there is a cosmic battle being waged between the forces of light and dark, good and evil, God and satan if you will. They call it the Warfare Worldview. There have been many scholarly books written on the subject and obviously plenty of the entertainment variety books and movies dished up for our pleasure. Clearly the concept is familiar to all of us.
Given the state of the world and the perpetual inability of science and reason to explain the problem of evil it must at least cross your mind from time to time. Some things are so vile that there is no rational explanation for the depravity we see in mankind other than evil itself. This is not a rejection of science at all, rather it's an admission that there are some things that can't be explained mathematically or molecular-ly. In my view it was when the intellectuals dismissed evil as a phenomenon made-up by "religious nuts" that the world came off it's tracks. Science is great and all, it just doesn't tie up everything into a nice knowable bow for us.
I don't advocate for "religion" either. Religion is more often itself a vessel for evil in the name of good. The difference maker is love. Not romantic love, or even brotherly love, but agape love. The essence of agape love is self-sacrifice. It is the exact opposite of evil. When you hear the answer God is love to the question of what is God think of the sacrifice of Jesus on the cross for the forgiveness of sin, all sin - that's love, agape love. God is love.
So you don't buy all that he died for your sins business, okay, that's your prerogative. Sometimes I think Jesus is for those who need him. I'm one of them, you may not be, your love may be strong and unshakable. But please don't dismiss agape love out of hand. If you have children you then you have given over to agape love... Yes, you understand...
In the battle for the human soul you have the two conduits that feed into it. One is the spirit the other the body, one ethereal and one earthly. What comes into the soul is projected out into the world through your thoughts, words and deeds. The innate part of you that knows what's good and right, fair and just comes from your spirit. Your lusts and base desires, like greed, gluttony, envy and violence is fed by your body. Uncontrolled this conduit is ripe for the invasion of evil.
Only practicing agape love and controlling your body's desires keep us from falling into perpetual darkness. Study this simple graphic to lock this concept into your psyche. It may be the difference in the war of light vs dark.
[click on the picture to enlarge]