All knowledge ultimately depends on Christ, and knowing Christ is intimately tied to growing in knowledge. Green shows how this is true in knowledge of nature, history, and ethics, as well as the spiritual life. Naturalism has no grounds for knowledge, he says.
For present purposes, though, the great contribution he makes in this book is showing how central knowing is to discipleship in Christ. Churches have lost track of that, and must recover it to regain our witness in the world.