In 1967, with the promulgation of Indulgentiarum Doctrina, Pope St. Paul VI revised the Church's law with respect to indulgences, the partial or plenary remission of temporal punishment incurred by sin that is already forgiven. Most people, including many Catholics, do not understand indulgences or believe them to be an old abuse of the medieval Church that led to the Protestant heresies. Yet Our Lord told the apostles, "Amen I say to you, whatsoever ye shall bind on the earth shall be bound in heaven, and whatsoever ye shall loose on the earth shall be loosed in heaven" (Matthew 18:18). One practical—and extremely important—application of this gift of Our Lord to Peter and the Church is that the Church may aid repentant sinners in supplying the penance they must do to make up for their sins (which must have already been forgiven, especially via the sacrament of Reconciliation). This is what indulgences are.

In New Regulations on Indulgences, Salvatorian Fr. Winfrid Herbst summarizes the changes made to the disciplines on indulgences made by St. Paul VI in the new Enchiridion Indulgentiarum from 1969. As such, this is a useful and practical guide for all those who would seek to learn how to gain partial and plenary indulgences for themselves and the souls in Purgatory. Above all, Fr. Herbst's work is invaluable to learn more about the principles and doctrines involved with indulgences and why they are extremely fruitful and beneficial not only for the remission of sins but, as St. Paul VI would say, for the enkindling of greater charity in the soul.