Tim Keller, Preaching: Communicating Faith in an Age of Skepticism (releases June 9), pages 159–160:

What the heart most wants the mind finds reasonable, the emotions find valuable, and the will finds doable. It is all-important, then, that preaching move the heart to stop trusting and loving other things more than God. What makes people into what they are is the order of their loves — what they love most, more, less, and least. That is more fundamental to who you are than even the beliefs to which you mentally subscribe. Your loves show what you actually believe in, not what you say you do. People, therefore, change not by merely changing their thinking but by changing what they love most. …

So the goal of the sermon cannot be merely to make the truth clear and understandable to the mind, but must also be to make it gripping and real to the heart. Change happens not just by giving the mind new arguments but also by feeding the imagination new beauties.

On a related note, find Keller’s lectures on preaching here.