In our natural bodies, there are many things inside that keep us alive, although we've never seen them. Antibodies, clotting agents, intestinal flora, white blood cells. Now, spiritually speaking, there are invisible forces at work that want to help us and save us, although other forces want to destroy us. Pastor Greg Laurie points out the work of God's Spirit acquaints us with our sin, and acquaints us with our Savior. It's important we know how to respond.