In The Dark Night of the Soul, Spanish mystic St. John of the Cross describes the purification, or "night," that the human soul must experience if it is to enter into loving union with God in this life. Its combination of personal, pastoral, and academic wisdom has made The Dark Night of the Soul an enduring classic in the literature of Christian spirituality. It is a book to which generations of readers, both lay and religious, have turned as they have sought to experience on earth the kind of intimacy with God that will characterize the lives of the blessed in heaven.