Abstinence leads one toward contemplation of the most exalted realities
1. Fasting is a special virtuous act of abstinence and according to St. Thomas it is principally realised for three reasons: first, to repress lusts or disordered passions, which in this way are unnerved. St. Jerome writes that “without Ceres and Bacchus, Venus cools down” (Contra Jovinianus, 2), that is to say that with abstinence in eating (Ceres) and in drinking (Bacchus), lust (Venus) subsides. Secondly, to incline the soul toward contemplation of the most sublime realities and declaring that one is more hungry for these than for the material ones. I had eaten no rich food, no meat or wine had entered my mouth, and I had not anointed myself at all, for the full three weeks. (Daniel 10:3) This is the meaning of Daniel’s three weeks of fasting, at the end of which he received revelation. Third, in reparation for sins. Conversion is not simply an interior fact which requires one to devote all of themselves, including physically. We read in Joel 2:12: “Yet even now, says the Lord, return to me with all your heart, with fasting, with weeping, and with mourning;” (Cf. Summa theologica, II-II, 147,1).
One might fast for a day or several days. Or one might simply skip a meal during the day. Spiritual writers also note that there are ways of fasting that do not necessarily involve food. An ancient Christian hymn for lent points out this fact: “Let us use sparingly words, food and drink, sleep and amusements. May we be more alert in the custody of our senses.”
St. Bernard of Clairvaux said that while fasting from food is a penance for the way sin entered the world — Adam and Eve’s disobedience to the command not to eat of the tree of knowledge of good and evil — one also can fast by keeping custody of the eyes (because sin often occurs by looking intentionally at certain things), the ears (because they often listen to vain talk) and the tongue (which so often is the instrument of sin through “defamation and gossip, from vain and useless words”). “Without such fasting, all other fasting is rejected by God,” St. Bernard said in a 12th century Lenten sermon.
2. Preface IV of Lent expresses these aims with the following words: “For through bodily fasting you restrain our faults, raise up our minds, and bestow both virtue and its reward”. In the same line St. Augustine on the usefulness of fasting says that “fasting purifies the soul, elevates the mind, submits the flesh to the spirit, makes the heart contrite and humiliated, dissipates the mists of concupiscence; dampen the ardor of lust and turn on the light of chastity” (De orat. et jeiun., serm 73).
3. The interior attitude of fasting, according to St. Thomas, is the “serenity of the soul”, “the inner joy” (la hilaritas mentis). It must be accomplished with a great love for the Lord and for the Church. If it were not done this would be only a constraint and a deprivation. And since when one gives himself, one is content, the Christian fast is characterised by a certain joy or inner serenity. This is why the Lord said: “And whenever you fast, do not look dismal, like the hypocrites, for they disfigure their faces so as to show others that they are fasting. Truly I tell you, they have received their reward.” (Matthew 6:16).
4. As we have already mentioned, fasting is an act of the virtue of abstinence. For it to be a virtuous act it is required that it be done reasonably. St. Thomas writes: “Right reason will never reduce food to the point of jeopardising the preservation of nature” (Summa theologica, II-II, 147, 1, ad 2). And “right reason does not reduce food enough to make a man unable to fulfil his duties” And to serve others. This is why a Christian will never stand before fasting to charity. Fasting remains a means of serving charity better. On the other hand, charity is the end of the whole Christian life.
5. St. Thomas writes: “It is the end (charity) the reality that must be drawn without measure. All this, instead, which is a means (fasting) in order to the end must be drawn with measure and proportion. Thus, for example, the doctor seeks the greatest possible health of the patient (the end). Instead administer the medicine (the medium) according to the capacity of the recipient. Well in the spiritual life the end is the love of God. Fasts, however, the vigils and all the other bodily exercises are not sought as an end, because the kingdom of God is not a question of food and drink (Romans 14:17), but as the means necessary to the end, that is to tame the concupiscences of the flesh, according to what the Apostle says: ‘but I punish my body and enslave it…’ (1 Corinthians 9:27). “And so these are used to measure a certain reason, such as that of desire immune nature and will not be extinguished”; [our translation] (Quodlibet., V, 9, 2).