And if the faithful offer indulgences in suffrage for the dead, they cultivate charity in an excellent way and while raising their minds to heaven, they bring a wiser order into the things of this world.
To recall briefly the most important considerations, this salutary practice teaches us in the first place how it is sad and bitter to have abandoned the Lord God. Indeed the faithful when they acquire indulgences understand that by their own powers they could not remedy the harm they have done to themselves and to the entire community by their sin, and they are therefore stirred to a salutary humility.
Furthermore, the use of indulgences shows us how closely we are united to each other in Christ, and how the supernatural life of each can benefit others so that these also may be more easily and more closely united with the Father. Therefore the use of indulgences effectively influences charity in us and demonstrates that charity in an outstanding manner when we offer indulgences as assistance to our brothers who rest in Christ.
Likewise, the religious practice of indulgences reawakens trust and hope in a full reconciliation with God the Father, but in such a way as will not justify any negligence nor in any way diminish the effort to acquire the dispositions required for full communion with God. Although indulgences are in fact free gifts, nevertheless they are granted for the living as well as for the dead only on determined conditions. To acquire them, it is indeed required on the one hand that prescribed works be performed, and on the other that the faithful have the necessary dispositions, that is to say, that they love God, detest sin, place their trust in the merits of Christ and believe firmly in the great assistance they derive from the Communion of Saints.
In addition, it should not be forgotten that by acquiring indulgences the faithful submit docilely to the legitimate pastors of the Church and above all to the successor of Blessed Peter, the keybearer of heaven, to whom the Saviour Himself entrusted the task of feeding His flock and governing His Church. The salutary institution of indulgences therefore contributes in its own way to bringing it about that the Church appear before Christ without blemish or defect, but holy and immaculate, admirably united with Christ in the supernatural bond of charity. Since in fact by means of indulgences members of the Church who are undergoing purification are united more speedily to those of the Church in heaven, the kingdom of Christ is through these same indulgences established more extensively and more speedily until we all attain to the unity of the faith and of the deep knowledge of the Son of God, to perfect manhood, to the mature measure of the fullness of Christ. (Papal Writings, Indulgentiarum Doctrina, 1967).