St. John Paul II describes how Christ’s act of redeeming us from slavery to sin is both a free gift and a task:
“In the mystery of Redemption, Christ’s victory over evil is given to us not simply for our personal advantage, but also as a task. We accept that task as we set out upon the way of the interior life, working consciously on ourselves—with Christ as our Teacher. The Gospel calls us to follow this very path. Christ’s call “Follow me!” is echoed on many pages of the Gospel and is addressed to different people—not only to the Galilean fishermen whom Jesus calls to become his Apostles (cf. Mt 4:19, Jn 1:43), but also, for example, to the rich young man in the Synoptic Gospels (cf. Mt 19:16-22, Mk 10:17:22, Lk 18:18-23). Jesus’s conversation with him is one of the key texts to which we must constantly return, from various points of view, as I did, for example, in the encyclical Veritatis Splendor.
“The call “Follow me!” is an invitation to set out along the path to which the inner dynamic of the mystery of Redemption leads us. This is the path indicated by the teaching, so often found in writings on the interior life and on mystical experience, about the three stages involved in “following Christ.” These three stages are sometimes called “ways.” We speak of the purgative way, the illuminative way, and the unitive way. In reality, these are not three distinct ways, but three aspects of the same way, along which Christ calls everyone, as he once called that young man in the Gospel.
“When the young man asks: “Teacher, what good deed must I do to have eternal life?”, Christ answers him: “If you wish to enter life, keep the commandments” (Mt 19:16 et passim). And when the young man continues to ask: “Which?” Christ simply reminds him of the principal commandments of the Decalogue, and especially those from the so-called “second tablet” concerning relations with one’s neighbor. In Christ’s teaching, of course, all the commandments are summarized in the commandment to love God above all things and one’s neighbor as oneself. He says so explicitly to a doctor of the Law in response to a question (cf. Mt 22:34-40; Mk 12:28-31). Observance of the commandments, properly understood, is synonymous with the purgative way: it means conquering sin, moral evil in its various guises. And this leads to a gradual inner purification.
“It also enables us to discover values. And hence we conclude that the purgative way leads organically into the illuminative way. Values are lights which illumine existence and, as we work on our lives, they shine ever more brightly on the horizon. So side by side with observance of the commandments—which has an essentially purgative meaning—we develop virtues. For example, in observing the commandment: “Thou shall not kill!” we discover the value of life under various aspects and we learn an ever deeper respect for it. In observing the commandment: “Thou shall not commit adultery!” we acquire the virtue of purity, and this means that we come to an ever greater awareness of the gratuitous beauty of the human body, of masculinity and femininity. This gratuitous beauty becomes a light for our actions. In observing the commandment: “Thou shall not bear false witness!” we learn the virtue of truthfulness. This not only excludes all lying and hypocrisy from our lives, but it develops within us a kind of “instinct for truth” which guides all our actions. And living thus in the truth, we acquire in our own humanity a connatural truthfulness.
“So the illuminative stage in the interior life emerges gradually from the purgative stage. With the passage of time, if we persevere in following Christ our Teacher, we feel less and less burdened by the struggle against sin, and we enjoy more and more the divine light which pervades all creation. This is most important, because it allows us to escape from a situation of constant inner exposure to the risk of sin—even though, on this earth, the risk always remains present to some degree—so as to move with ever greater freedom within the whole of the created world. The same freedom and simplicity characterizes our relations with other human beings, including those of the opposite sex. Interior light illumines our actions and shows us all the good in the created world as coming from the hand of God. Thus the purgative way and then the illuminative way form the organic introduction to what is known as the unitive way. This is the final stage of the interior journey, when the soul experiences a special union with God. This union is realized in contemplation of the divine Being and in the experience of love which flows from it with growing intensity. In this way we somehow anticipate what is destined to be ours in eternity, beyond death and the grave. Christ, supreme Teacher of the spiritual life, together with all those who have been formed in his school, teaches that even in this life we can enter onto the path of union with God.”
— St. John Paul II – Memory and Identity Rizzoli 2005: