In addition to the purification of the memory (which tends to tenaciously hold on to harmful memories which impede spiritual growth), Saint John of the Cross also calls for a purification of the imagination. A purification of the imagination is needed because the mind becomes polluted when the imagination is used for sinful and evil purposes.

A first step in purifying the imagination is simply to mortify its attempt to imagine sinful pleasures or harmful actions. In this sense there is an active purification of the mind by way of a virtue driven custody of the imagination. The more we cut off the evil inclination of the imagination at its first movement toward sin, the more we rewire the imagination to act in a virtuous manner.

A second and powerful step to purify the imagination is to use the imagination as a method of meditation on the life and mysteries of Jesus Christ. In this manner we begin to use the imagination in an incredibly useful and sanctifying manner.

 All of the mysteries of Christ’s life are potent sources of grace. Thus, meditating on the mysteries of Christ’s life does a “real work” in our souls. The faculty of the imagination is useful in this regard because we can use the imagination to “mystically transport” us back to the side of Christ in all of his mysteries. The Saint who particularly recommended this method of meditation on the mysteries of Jesus’ life by utilizing the imagination is Ignatius of Loyola. His book of Spiritual Exercises contains a series of meditations where you imaginatively enter into the mysteries of Jesus’ life and even converse with Jesus (or Mary) pertaining to the mystery in question. This method of meditation can be profoundly transformative and purifying.