The people of God in Isaiah’s day had starved their imagination by looking on the face of idols, and Isaiah made them look up at the heavens, that is, he made them begin to use their imagination aright. Nature to a saint is sacramental. If we are children of God, we have a tremendous treasure in Nature. In every wind that blows, in every night and day of the year, in every sign of the sky, in every blossoming and in every withering of the earth, there is a real coming of God to us if we will simply use our starved imagination to realize it.
The test of spiritual concentration is bringing the imagination into captivity. Is your imagination looking on the face of an idol? Is the idol yourself? Your work? Your conception of what a worker should be? Your experience of salvation and sanctification? Then your imagination of God is starved, and when you are up against difficulties you have no power, you can only endure in darkness. If your imagination is starved, do not look back to your own experience; it is God Whom you need. Go right out of yourself, away from the face of your idols, away from everything that has been starving your imagination. Rouse yourself, take the gibe that Isaiah gave the people, and deliberately turn your imagination to God.
One of the reasons of stultification in prayer is that there is no imagination, no power of putting ourselves deliberately before God. We have to learn how to be broken bread and poured out wine on the line of intercession more than on the line of personal contact. Imagination is the power God gives a saint to posit himself out of himself into relationships he never was in.