The structural elements of the plot — two pairs of young lovers, obstructive parents, clever servants, fools who believe themselves wise, and the role of mistaken identity in frustrating the oppressive plans of the older generation — all have deep roots in the Western comic tradition. But an ingredient that Sheridan adds to this familiar mixture is the role of wine as an index to a character’s sanity. The play opens with Ferdinand’s servant, Lopez, wondering aloud at the very different behaviour of the upper classes when they fall in love:

. . . my love and my master’s differ strangely — Don Ferdinand is much too gallant to eat, drink or sleep — now, my love gives me an appetite — then I am fond of dreaming of my mistress, and I love dearly to toast her — This cannot be done without good sleep, and good liquor, hence my partiality to a feather bed, and a bottle —

Sheridan himself had a foot in both these camps. His courtship of his first wife, Elizabeth, was marked by the high romantic trappings of duels, elopement, and implacable parents. But he seems never to have followed Ferdinand down the path of abstinence — when it came to drink, he was firmly on Lopez’s side. The famous trio sung at almost the pitch of comic complication in Act II by Jerome, Isaac, and Ferdinand praises the power of wine to compose differences:

A bumper of good liquor,
Will end a contest quicker,
Than justice, judge or vicar.
        So fill a cheerful glass,
        And let good humour pass.
But if more deep the quarrel,
Why, sooner drain the barrel,
Than be the hateful fellow,
That’s crabbed when he is mellow.

This was certainly Sheridan’s personal philosophy, and the denouement of the play gives it a surprising human depth. His plans for his children foiled, Jerome ceases to struggle against the natural and inevitable: “Egad, I believe I shall grow the best humour’d fellow in Spain.” He opens his doors to all comers, promises an evening of “wine and dance”, and expresses the wisdom of accepting what has occurred in a final metaphor of drinking: “Our children’s weddings are the only hollidays that age can boast, and then we drain with pleasure, the little stock of spirits time has left us.”

In The Duenna wine produces a natural intoxication in which a temporary forgetfulness of the self can console us for, and occasionally rescue us from, the much more deadly consequences of infinitely more dangerous intoxicants of our own manufacture — that is to say, those delicious but conceited delusions which whisper to us that we are really much better looking, more intelligent, wittier, more subtle, and in a word simply better, than our fellowmen.