The author says, "Preaching draws the Christian outside of self and into Christ, in whom we have real freedom."

Where lies the power to change souls so? Jesus said, "No one can come to me unless the Father who sent me draws him." (John 6:44 ESV)

And elsewhere we read, "So neither he who plants nor he who waters is anything, but only God who gives the growth." (1 Cor. 3:7 ESV)