First, the author makes it clear that this book is neither a work of apologetics nor an expression of her personal religious beliefs, but a commentary on particular statements contained in Christian creeds. The specific statements she addresses are those regarding the nature of God, especially in His capacity as Creator. Her intention is to show how these characteristics attributed to God are applicable to the human mind engaged in imaginative creation as well.
Sayers acknowledges that many people find the doctrine of the Trinity difficult to grasp, but explains that Trinitarian structures are, in fact, not foreign to our experience. She cites as examples the trinity of sight: the form seen, the act of vision, and the mental correlation of the two; and the trinity of thought: memory, understanding, and will. The Trinity then becomes the basis for insight into the mind of the maker:
“For every work [or act] of creation is threefold, an earthly trinity to match the heavenly. First…there is the Creative Idea…and this is the image of the Father. Second, there is the Creative Energy…and this is the image of the Word. Third, there is the Creative Power…and this is the image of the indwelling Spirit.
And these three are one, each equally in itself the whole work, whereof none can exist without the other: and this is the image of the Trinity.”
Several chapters are then devoted to further examination of these elements, culminating in an acknowledgement that although the perfect co-equality of the Divine Trinity is represented by an equilateral triangle, the trinity of the human maker is typically scalene, sometimes fantastically irregular. In conclusion, Sayers addresses the question of how man may deal with life creatively, whatever his occupation.