Believers need to grow simultaneously in two areas: an awareness of what responses God deserves, and an awareness of how works of imagination communicate. To fail in the first area is to allow the profane, the blasphemous and the false to enter the Christian imagination, by virtue of not knowing God as He is. To fail in the second area is to allow the cheap, the trivial, the shallow, the irreverent, and the sentimental to enter the Christian imagination by virtue of imbibing pop culture as our imaginative lingua franca. Both are dangerous and insidious. In the first, we may offend God because we do not realise who He is (Psalm 50:21). In the second, we may offend God because we do not consider what our symbolic actions are communicating (Malachi 1:6-14).
If Christians should grow in their ability to discern superior Christian works of imagination, how should they do this? Must every Christian pursue some kind of music appreciation, literary criticism or aesthetic theory in order to recognise Christian from non-Christian or sub-Christian imagination? Likely not, though no Christian should scorn the pursuit of knowledge, wisdom and understanding, particularly in those areas that communicate a Christian outlook.
Instead, Christians can pursue better understanding in these areas by becoming attentive to the form of music, poetry, literature, painting, sculpture, history, or other humanities that shape imagination. By form, we mean its actual shape and composition: the sum total or result of its components parts that communicate its message, be those colours, shapes, notes, harmonies, or words.
One way to approach this is to use the idea of proportion or scale. Consider a miniature. A miniature car, ship, plane, or village pleases us because it preserves the proportions of the original object in a much smaller scale. The better the proportions, the truer the miniature as a scaled-down version of the original. In many ways, works of imagination function similarly. Metaphors reduce the large-scale realities of God, the world, and self to a miniature version of a poem, a hymn, a symphony, a novel, an allegory, a sculpture, a painting, or another work of imagination. Of course, the work of imagination can never be a miniature of all of reality. Instead, it seeks to faithfully capture some small section of reality: a truth, an affection, an ethical obligation or some other reality. Imaginative materials are not (typically) metal, plastic, or paint. They are words, poetic tropes, meter, notes, melodies, harmonies, rhythms, tone colours, narrative genres, plots, characters, dialogues, paints, oils, and so forth.