Objection 1. It would seem that drunkenness is not a sin. For every sin has a corresponding contrary sin, thus timidity is opposed to daring, and presumption to pusillanimity. But no sin is opposed to drunkenness. Therefore drunkenness is not a sin.
Objection 2. Further, every sin is voluntary [Augustine, De Vera Relig. xiv]. But no man wishes to be drunk, since no man wishes to be deprived of the use of reason. Therefore drunkenness is not a sin.
Objection 3. Further, whoever causes another to sin, sins himself. Therefore, if drunkenness were a sin, it would follow that it is a sin to ask a man to drink that which makes him drunk, which would seem very hard.
Objection 4. Further, every sin calls for correction. But correction is not applied to drunkards: for Gregory [Cf. Canon Denique, dist. 4 where Gratian refers to a letter of St. Gregory to St. Augustine of Canterbury] says that "we must forbear with their ways, lest they become worse if they be compelled to give up the habit." Therefore drunkenness is not a sin.
On the contrary, The Apostle says (Romans 13:13): "Not in rioting and drunkenness."
I answer that, Drunkenness may be understood in two ways. First, 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. On this sense drunkenness denotes not a sin, but a penal defect resulting from a fault. Secondly, drunkenness may denote the act by which a man incurs this defect. This act may cause drunkenness in two ways. On one way, 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 Genesis 9. On 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 (Romans 13:13).
Reply to Objection 1. As the Philosopher says (Ethic. iii, 11), insensibility which is opposed to temperance "is not very common," so that like its species which are opposed to the species of intemperance it has no name. Hence the vice opposed to drunkenness is unnamed; and yet if a man were knowingly to abstain from wine to the extent of molesting nature grievously, he would not be free from sin.
Reply to Objection 2. This objection regards the resulting defect which is involuntary: whereas immoderate use of wine is voluntary, and it is in this that the sin consists.
Reply to Objection 3. Even as he that is drunk is excused if he knows not the strength of the wine, so too is he that invites another to drink excused from sin, if he be unaware that the drinker is the kind of person to be made drunk by the drink offered. But if ignorance be lacking neither is excused from sin.
Reply to Objection 4. Sometimes the correction of a sinner is to be foregone, as stated above (Question 33, Article 6). Hence Augustine says in a letter (Ad Aurel. Episc. Ep. xxii), "Meseems, such things are cured not by bitterness, severity, harshness, but by teaching rather than commanding, by advice rather than threats. Such is the course to be followed with the majority of sinners: few are they whose sins should be treated with severity."
Source: Summa Theologica (New Advent)