"Mansfield Park." Partisan Review 21 (September-October 1954): 492-511. Also published in Encounter, September 1954: 9-19.

Excerpt:

Sooner or later, when we speak of Jane Austen, we speak of her irony, and it is better to speak of it sooner rather than later because nothing can so far mislead us about her work as a wrong understanding of this one aspect of it. Most people either value irony too much or fear it too much. This is true of their response to irony in its first simple meaning, that of a device of rhetoric by which we say one thing and intend its opposite, or intend more, or less, than we say. It is equally true of their response to irony in its derived meaning, the loose generalized sense in in which we speak of irony as a quality of someone’s mind, Montaigne’s for example. Both the excessive valuation and the excessive fear of irony lead us to misconceive the part it can play in the intellectual and moral life. To Jane Austen, irony does not mean, as it means to many, a moral detachment or the tone of superiority that goes with moral detachment. Upon irony so conceived she has made her own judgment in the figure of Mr. Bennet of Pride and Prejudice, whose irony of moral detachment is shown to be the cause of his becoming a moral nonentity.

Online:
Google Books - essay in The Moral Obligation to be Intelligent
Boston University - Partisan Review archive - first published version
Unz.org - full text from Encounter [pdf]