The mystery which is beyond understanding is likewise beyond imagination. The exercise of imagination upon the mysteries of faith is a necessary and wholesome process: it is part of mental prayer. But the result remains quite inadequate to the object. Forgetting this piece of psychology, people take for objectively incredible that which is subjectively unimaginable: and the childish shortcomings and vagaries of the imagination are mistaken for absurdities in the mystery proposed for belief, as a boy astronomer might mistake the effect of chromatic aberration in his telescope for colours in the stars. Dulness of imagination is a great obstacle to religious belief.
Of God and His Creatures: 4.1