Aquinas argues that
drunkenness is a mortal sin, because then a man willingly and knowingly deprives himself of the use of reason, whereby he performs virtuous deeds and avoids sin, and thus he sins mortally by running the risk of falling into sin.
On the other hand, Aquinas also argues that sleep suspends the use of reason:
What a man does while asleep, against the moral law, is not imputed to him as a sin; as Augustine says (Gen. ad lit. xii, 15). But this would not be the case if man, while asleep, had free use of his reason and intellect. Therefore the judgment of the intellect is hindered by suspension of the senses.
One might try to reconcile the two claims by saying that sleep is something that befalls us involuntarily, and that it would be wrong to willingly and knowingly go to sleep. But that would not fit with ordinary human practice, and would contradict Aquinas’ own rejection of the claim that it is “against virtue for a person to set himself to sleep”. Moreover, Aquinas notes without any moral warnings that sleep—like baths, contemplation of the truth and other apparently quite innocent things—assuages sorrow.
So what’s going on?
And to add a further complication, Proverbs 31:6 seems to recommend the use of alcohol as an analgesic.
I can think of three things one could say on behalf of Aquinas.
First, one might attempt a Double Effect justification. In sleep, the body rests. Aquinas certainly thinks so: the discussion of the suspension of reason during sleep presupposes that the primary effect of sleep is on the body. It is this bodily rest, rather than the suspension of reason, that is intended. One might worry that the suspension of reason is a means to rest. However, non-human animals, who lack reason in Aquinas’s sense of the word, also sleep. Presumably whatever benefits they derive from the sleep are available to us, and it seems not unlikely that many of these do not depend on the suspension of reason. Similarly, alcohol helps with pain in non-human animals, and so the mechanism by which it helps may not depend on the suspension of reason.
That said, I don’t think Aquinas would want to take this approach (though it may well work for me). For Aquinas thinks that it is stupid we cannot claim that an invariable or typical effect of something intended counts as unintended (Commentary on the Physics, Book II, Lecture 8, paragraph 214). But the suspension of reason is indeed an invariable or typical effect of sleep.
A second approach focuses on Aquinas’ response to the question of why the loss of rationality during the sexual act does not render the sexual act wrong, from which I already quoted the rejection of the claim that it’s vicious to set oneself to sleep:
it is not contrary to virtue, if the act of reason be sometimes interrupted for something that is done in accordance with reason … .
This approach does not seem to be based on Double Effect, but rather on some sort of principle that it is permissible to suspend a good for the sake of that same good. This principle applies neatly to sleep as well as to the biblical case of analgesic use of alcohol (given that reason opposes suffering the pain).
But this approach would also moderate Aquinas’s seemingly absolute rejection of drunkenness. For we can imagine cases where it seems that reason would recommend drunkenness, such as when a tyrant will kill you if you refuse to get drunk with them. And once one allows drunkenness in such extreme cases, what is to prevent allowing it in more moderate cases, such as getting drunk with one’s boss in the hope of getting a deserved promotion… or maybe just for fun? Aquinas can say that these cases are immoral and hence against reason, but that would beg the question.
A third approach would note that sleep, unlike drunken stupor, is a natural human state, and information processing in sleep is itself a part of our human rational processing. However, while this gives a neat explanation of why it’s permissible to set oneself to sleep, it doesn’t explain the permissibility of the analgesic use of alcohol or, more significantly in modern times, of the use of general anaesthesia during medical procedures.
A different approach for justifying sleep, the analgesic use of alcohol and general anaesthesia insists that temporary suspension of a good is different from willful opposition to the good. To eat in an hour rather than now does not oppose the good of food. The down side of this fourth approach is that it seems to destroy Aquinas’s argument against drunkenness as opposed to the good of reason. And it seems to let in too much: can’t one say that by torturing someone, one is merely suspending their painless state?
I think the best philosophical solution is the first, Double Effect. Aquinas alas can’t use it because his version of Double Effect is too narrow, given his view that typical effects of intended things count as intended.
