Summa: II, ii, 148, 1.
Article 1. Whether gluttony is a sin?
Objection 1. It would seem that gluttony is not a sin. For our Lord said: Not that which goeth into the mouth defileth a man. (St. Matt. xv. 11) Now gluttony regards food which goes into a man. Therefore, since every sin defiles a man, it seems that gluttony is not a sin.
Gluttony should not be considered as a sin since it relates to what goes into and does not come out of a man. Since no external and visible created thing is evil but good by nature because created by God, gluttony should not be considered a sin by reason of its object.
Objection 2. Further, No man sins in what he cannot avoid (Ep. lxxi, ad Lucin). Now gluttony is immoderation in food; and man cannot avoid this, for Gregory says: Since in eating pleasure and necessity go together, we fail to discern between the call of necessity and the seduction of pleasure (Moralia, xxx. 18), and Augustine say, Who is it, Lord, that does not eat a little more than necessary? (Confessions x, 31) Therefore gluttony is not a sin.
Because gluttony relates to a natural and necessary appetite, it should not be counted as a sin. Every man falls and stumbles in the presence of good food or fine wine. Man needs to eat to survive and so can rarely differentiate between what is needed and what is desired. Because this particular good is so necessary a man for whom it easily becomes his delight cannot be accounted sinful.
Objection 3. Further, in every kind of sin the first movement is a sin. But the first movement in taking food is not a sin, else hunger and thirst would be sinful. Therefore gluttony is not a sin.
The first movement in any sin is the cause of the sin. It would appear that the first cause in eating is hunger and thirst. Hunger and thirst are necessary causes of a man’s perfection of his whole nature. Therefore gluttony is not a sin.
On the contrary, Gregory says that unless we first tame the enemy dwelling within us, namely our gluttonous appetite, we have not even stood up to engage in the spiritual combat. (Moralia. xxx. 18) But man’s inward enemy is sin. Therefore gluttony is a sin.
Appetite is not a sin. Exaggerated appetite is a sin. Unless we begin to find the mean between the extremes of gorging and fasting, our bodies shall not be conditioned properly to house the soul that is made to seek after God. The problem is not with appetite per se but with the internal enemy that would drive appetite to an extreme expression. The inward enemy is the spirit that perverts and corrupts the appetite.
I answer that, Gluttony denotes, not any desire of eating and drinking, but an inordinate desire. Now desire is said to be inordinate through leaving the order of reason, wherein the good of moral virtue consists: and a thing is said to be a sin through being contrary to virtue. Wherefore it is evident that gluttony is a sin.
So Gluttony is an expression of an intemperate or overindulgent will. When the will and its desire are ‘inordinate’, a man ignores the rational end for which the natural good of the body is pursued and so exaggerates its need. So rather than ordering his relation to food and drink, he rashly and impetuously overindulges them. The cause is normally a kind of irrational intention to procure from them what they have forfeited in the loss of reason, i.e. some kind of imitation of divine satisfaction. Such is, of course, not only irrational but insane. Thus, gluttony (and drunkenness) is a sin.
Reply to Objection 1. That which goes into man by way of food, by reason of its substance and nature, does not defile a man spiritually. But the Jews, against whom our Lord is speaking, and the Manichees deemed certain foods to make a man unclean, not on account of their signification, but by reason of their nature. It is the inordinate desire of food that defiles a man spiritually.
The Jews and Manichees deem certain foods to be evil in nature. No food is evil in nature since all food comes from God’s good creation of it. But to make food or drink into evil natures is just as sinful as making an idol out of them. Food and drink are necessary to the redemption of the whole person in so far as they enable a man to survive for long enough to seek God, find Him, and become right with Him. So both those who abstain from food and drink because they are deemed evil and also those who overindulge them because they are ‘too good’ are to be counted guilty of gluttony.
Reply to Objection 2. As stated above, the vice of gluttony does not regard the substance of food, but in the desire thereof not being regulated by reason. Wherefore if a man exceed in quantity of food, not from desire of food, but through deeming it necessary to him, this pertains, not to gluttony, but to some kind of inexperience. It is a case of gluttony only when a man knowingly exceeds the measure in eating, from a desire for the pleasures of the palate.
Those who overeat and overdrink are often transparently aware of their sin. So they knowingly overeat and overdrink. Otherwise they wouldn’t be closeted over-eaters and over-drinkers. In public such people often eat or drink less. Such is an outward and visible sign that the sins of gluttony loom large within their souls. But ‘what they do in secret is known openly.’ So they habituate their palates to an overdependence upon food or drink. Thus a basic need become a desire and the body becomes dependent upon a false god.
Reply to Objection 3. The appetite is twofold. There is the natural appetite, which belongs to the powers of the vegetative soul. On these powers virtue and vice are impossible, since they cannot be subject to reason; wherefore the appetitive power is differentiated from the powers of secretion, digestion, and excretion, and to it hunger and thirst are to be referred. Besides this there is another, the sensitive appetite, and it is in the concupiscence of this appetite that the vice of gluttony consists. Hence the first movement of gluttony denotes inordinateness in the sensitive appetite, and this is not without sin.
The first movement of gluttony is not found in the vegetative soul but in the sensitive soul. The vegetative soul is the seat of instinctually present needs or bodily appetites. The sensitive soul is the seat of the powers of perception and willful movement. Here a man has the power of imagination, common sense, evaluation and estimation, and memory. So through the sensitive soul a man can, to a degree, order his relation to the external world. Were he to trust his senses wholly he would neither over-eat nor over-drink since he would remember that they make him sick. But the habituation to intemperance has a strange effect upon the mind which jumps to delight against pain and pleasure. Thus a man perverts his sensitive appetite through a contortion of reason. The corporeal world has been exaggerated by reason that dissociates delight from necessity. So the sensitive soul as mediator between the rational and vegetative souls is corrupted. Thus gluttony is a sin.