"A Modest Proposal" is one of the greatest works of satire ever published; the concept of civilized man raising children to eat is so abominable and rediculous that it is easily dismissed, and yet Swift, writing as some ultra-utilitarian economist, makes extremely logical points in favor of the idea. Irony is present in the essay from the title onwards; the proposal is anything but "modest," and is in fact horrifying to consider. Swift leans heavily on the emotional argument, explaining:
There is likewise another great advantage in my scheme, that it will prevent those voluntary abortions, and that horrid practice of women murdering their bastard children, alas! too frequent among us, sacrificing the poor innocent babes, I doubt, more to avoid the expence than the shame, which would move tears and pity in the most savage and inhuman breast.
(Swift, "A Modest Proposal," gutenberg.org)
Of course, the correlation is silly at best; adding cannibalism to what was a terrible crime during that era doesn't exactly add moral value. Swift's use of language is key; while he writes in the first-person narrative common at the time, he also cites facts and figures to back up his points. This allows the essay to satirize not only what Swift saw as the inhumane treatment of the Irish by the English, but also the common view that "Papists," followers of the Roman Catholic Church rather than the Church of England, were somehow less-than-human.