[OnyxCougar]

I think that everything has an opposite.

Therefore if there is a God that represents love, creation, truth, compassion and justice, there is an opposite force (a "devil") that represents hate, destruction, lies, indifference and injustice.

In the Christian mindset, the devil is not as powerful as God, because Lucifer was once an angel, created by God. This means that ultimately, Good will triumph over Evil, as good is (in the long run) more powerful than evil. This is then further ensured by Jesus' sacrifice and ascension, enabling him to come back to earth and meet Lucifer face to face, and subduing him.

Other pantheons have similar concepts in different forms, but the idea in most is centered on good vs. evil. If you do good, you will advance, be rewarded. If you do evil, you will not advance, be punished.

It is the timeless struggle.