Say you drink and you know if you drink more you might get drunk, or you simply drink to get drunk. You will become drunk and you know it, and no one is forcing you to drink.
Is that a sin, according to the Roman Catholic Church?
The short answer is, if you are trying to get drunk on purpose, then the answer is basically “yes.” That is a sin, and a grave (mortal) one.
The Catechism of the Catholic Church is very concise on this point, and simply says,
The virtue of temperance disposes us to avoid every kind of excess: the abuse of food, alcohol, tobacco, or medicine. Those incur grave guilt who, by drunkenness or a love of speed, endanger their own and others' safety on the road, at sea, or in the air (No. 2290).
From the natural law point of view, however, one can fairly easily discern that the fundamental problem with getting drunk is intoxication: drinking too much alcohol leaves a person in a state in which his behavior is unpredictable and potentially dangerous, for himself or for others. (Said in more classical terms, the body and the emotions are no longer under the control of reason.)
Since the potential danger of harm to self and others is significant and grave, it follows that deliberately getting drunk is itself a grave offense.
One might also add that drunkenness (and intoxication in general), which incapacitates reason while leaving the lower faculties without guidance, is a particularly grave affront to the very constitution, or nature, and dignity of the man who makes himself drunk. Man is not simply an animal; his soul is spiritual and rational. It is precisely his rationality that makes him emerge above all the other animals. And unfortunately, rationality is precisely what intoxication targets.
(See my fuller treatment of intoxication as an answer to a question about the morality of drugs, as opposed to alcohol and tobacco.)
The Scriptures attest abundantly to the gravity of drunkenness. For example:
Let us conduct ourselves becomingly as in the day, not in reveling and drunkenness … (Rom. 13:13).
I wrote to you not to associate with any one who bears the name of brother if he is guilty of immorality or greed, or is an idolater, reviler, drunkard, or robber—not even to eat with such a one (1 Cor. 5:11).
Neither … thieves, nor the greedy, nor drunkards, nor revilers, nor robbers will inherit the kingdom of God (1 Cor. 6:9-10).
… envy, drunkenness, carousing, and the like. I warn you, as I warned you before, that those who do such things shall not inherit the kingdom of God (Gal. 5:21).
And do not get drunk with wine, for that is debauchery; but be filled with the Spirit (Eph. 5:18).
A bishop must be … no drunkard, not violent but gentle, not quarrelsome, and no lover of money (1 Tim. 3:2-3).
For a bishop, as God’s steward, must be blameless; he must not be arrogant or quick-tempered or a drunkard … (Titus 1:7).
(Source: article from Catholic Answers.)
One could imagine edge cases in which even ingesting large quantities of alcohol is moral (e.g., in an extreme medical emergency, such as when surgery must be done in the field, it could be used as an emergency anesthetic), but these are exceedingly rare and singular.
In any event, it is clear that deliberately and voluntarily drinking to the point of drunkenness is gravely immoral.
St. Thomas Aquinas explains (Summa Theologica II-II q. 150 a. 1 c.):
Drunkenness may be understood in two ways.
- it may signify the defect itself of a man resulting from his drinking much wine, the consequence being that he loses the use of reason. In this sense drunkenness denotes not a sin, but a penal defect resulting from a fault.
- drunkenness may denote the act by which a man incurs this defect. This act may cause drunkenness in two ways.
- through the wine being too strong, without the drinker being cognizant of this: and in this way too, drunkenness may occur without sin, especially if it is not through his negligence, and thus we believe that Noah was made drunk as related in Gn. 9.
- In another way drunkenness may result from inordinate concupiscence and use of wine: in this way it is accounted a sin, and is comprised under gluttony as a species under its genus. For gluttony is divided into "surfeiting [Douay:,'rioting'] and drunkenness," which are forbidden by the Apostle (Rm. 13:13).
There's also Ga 5:19-21 (taken from this answer):
Now the works of the flesh are manifest, which are fornication, uncleanness, immodesty, luxury, Idolatry, witchcrafts (φαρμακία), enmities, contentions, emulations, wraths, quarrels, dissensions, sects, Envies, murders, drunkenness, revellings, and such like. Of the which I foretell you, as I have foretold to you, that they who do such things shall not obtain the kingdom of God.