I just finished reading an article by Alex Chediak in which he summarizes a lecture by R.C. Sproul on the existence of evil. I highly recommend that you read this summary. It is good to understand these kinds of concepts so that you have a better understanding of how powerful and essential the Gospel really is. Here is an excerpt from the summary:

In our culture we get the idea that evil is some sort of independent substance, that evil exists in and of itself and that it influences the affairs of our life and of this world. But evil is not a thing that has existence. Evil has no being.  It has no ontological status. Rather evil is an action of something that is a thing. I am something, you are something, and when I do something that is not good, then I am doing something that is evil.  Evil, then, is the activity of a being.  But it itself has no being.

And here is the summary in its entirety: http://bit.ly/atyqyh