When it comes to believing, it would seem that our cognitive beliefs are often separated from our actions. And that kind of belief has become what matters. There is who we are and then there is what we believe often having nothing to do with one another.
This is what the writer was getting at when he said, "faith without works is dead..." and what Paul is referring to when he says, "...the only thing that counts is faith expressing itself through love."
The kind of belief that Christianity holds to is a belief that transforms, it changes the way one lives and is more of a lifestyle than thoughts about life. It is not merely abstract thoughts a person holds to or can speak about. This "abstract" belief system is what allows me to affirm certain things about the teachings of the bible and yet live a life that contradicts them.
Peter Rollins writes about how we believe we are what we believe (he says it better). In other words, believing in Christianity often allows us to live a life that denies Christianity, because we perceive ourselves by our "right" beliefs rather than our actions. It is in this way we can participate in the very actions and systems that we are supposedly against.