Doing penance requires explanation for twenty-first century Catholics. What is accomplished by the traditional Lenten practices, they may inquire. Of course, socially-minded Catholics might find almsgiving an intelligible practice. After all, many of our people think of the Church mainly as an eleemosynary institution. A place for donations. Prayer also may be familiar to contemporary churchgoers. Still, most would find it difficult to identify what is penitential about praying. Many Catholics in fact consider prayer something useful for themselves. Prayer calms and consoles and comforts... Then comes fasting. Why should the Catholic fast? Few of our co-religionists would be able to come up with a good answer.
This widespread nescience did not exist among devout or even not so devout Catholics fifty years ago. Pre-conciliar Catholic culture embraced the Church’s fasting discipline. Even secular magazines and newspapers advertised Lenten menus and recipes. Truth to tell, today’s popular items such as Lobster Mac owe their existence to that once favorite of Catholic Friday-night suppers, the pre-gentrified macaroni and cheese. For about a century of their history in the United States, Catholics were commonly and derisively called “Mackerel-Snappers.” Protestants distrusted the Friday abstinence, though fresh fish stores prospered–at least along the coastlines– in Catholic neighborhoods. Catholics themselves were schooled in the mechanics of fasting. How much one could eat at the “light meal” caused concern to both young and old alike. Each adult Catholic was required to seek a dispensation from his or her confessor before modifying the Lenten regulations. Fasting was part of being Catholic. Moreover, the rationale for this practice was imbedded into the minds of Catholics by teaching sisters, mission preachers, and the parish clergy who were responsible for both advertising the Lenten rules and dispensing, when the cause was legitimate, from them. Casusitic fasting may have passed away, but virtuous fasting remains one of the principal penances that Catholics undertake during Lent.
Because practices without reasons behind them are wont to disappear, we need to retrieve the spiritual benefits of fasting. The standard reasons given for fasting enjoy a long pedigree in the Western Christian tradition. Aquinas summarizes the common wisdom of the Church: fasting, he says, promotes “the prevention of spiritual ills and the pursuit of spiritual blessings.” How?
Fasting, as every Catholic schoolchild in 1950 knew, makes us better Christians. Three considerations emerge. Fasting first of all bridles the lusts of the flesh. Aquinas takes the connection between abstinence and chastity as a matter of common sense. Even the comic Latin poet, Terence, has observed that “Venus freezes when Ceres and Bacchus are away.” Ceres and Bacchus of course are the gods of grain and grape. Secondly, fasting aids contemplation and study. In a word, when a person fasts, the mind works better. The mind studies better. The mind prays better. Common experience suffices to make the point. Who would suppose that one passes seamlessly from indulging in sensual excess, for instance, lechery or drunkenness, to practicing contemplative prayer? One of the biggest errors advanced by marginal theologians of the 1960s and 70s concerns God and the human body. Many argued that sensual experiences foster union with God. Not a little unhappiness resulted from this experiment.
Thirdly, fasting effects satisfaction for sin. Little today is said about satisfaction for sin. We all tend to presume on God’s mercy. The truth is that sin erodes something of the human good in the sinner. Forgiveness is one thing; restoring lost virtue entails another. In a word, activities that involve suffering can be either chosen or accepted as satisfactory for sin. The privations that suffering brings restores our character softened by sin. The man who has been generous with courtesans now gives alms to the poor. The proud man may renounce even legitimate honors. Christian satisfaction suffuses the Lenten season. If there were not an explanation for the things that Christ suffered, then he could appear as a bumbler or a man out-of-luck. Were Christ’s sufferings to remain a complete mystery, why urge people to imitate them? Priests especially need to know why Christ’s sufferings are salvific. There are two ways to find out. One is study. That can take time. The other is imitation. The easiest way to begin is by fasting during Lent. Then the priest will discover the satisfactory character of almsgiving and prayer. He will also be able to explain to his people why “whoever loses his life for [Christ’s] will save it” (Lk 9: 24).
 Summa theologiae IIa-IIae q. 147, art. 1, ad 2.
 Summa theologiae IIa-IIae q. 147, art. 1. Citing Saint Jerome Adversus Jovinianum II (PL 23, 310).