Here's a very, very good post on imagination in Christian perspective. (HT: Dan Edelen) This one is worth reading - slowly - all the way through - twice.

If we are going to talk about the ‘primacy’ of anything in man’s grasping of his world, let us speak of the primacy of the imagination. The very act of perceiving our world necessarily involves the imagination. There is no such thing as mere perception.

It so happens that Peter Kreeft also has an excellent lecture on this.