Jonathan Swift in A Modest Proposal utilizes a number of rhetorical strategies and devices in order to convince the English and the Irish that they can take action to reduce the abject poverty many were experiencing in Ireland in the eighteenth century.
To begin, the title of his work is itself an understatement. The pamphlet’s full title is
A Modest Proposal for Preventing the Children of Poor People from Being a Burthen to their Parents, or the Country, and for Making them Beneficial to the Publick.
The title establishes the problem that will be discussed in the actual pamphlet, the fact that the children of poor people are a burden to their parents and to the country. To call a proposal that solves this rather large and complicated problem "modest" is an understatement. Swift likely uses the understatement to get the reader’s attention and to let the reader know the forthcoming proposal will be satirical.
Then, as Swift begins to offer the context for his argument, the reader immediately learns the speaker is not Swift himself but an economic "prospector" who has studied the problem of poverty and is ready to provide solutions. This use of a persona serves two purposes. It gives Swift the ability to deliver his message through a credible source, one who understands the economy and is studied in the current problem. It also, and perhaps more importantly, gives Swift some distance from the actual proposals he will make, which as the speaker himself notes, will be found offensive by many.
As the prospector begins to describe the problem of poverty in Ireland, he calls it a “melancholy object” and describes the conditions of the women and children as they beg for alms on the street. This is a direct appeal to emotion and pity in his reader. Satirically, though, he goes from this emotional appeal directly to hyperbole, suggesting that the children who pose the biggest burden to their parents and the state are those who are too young to steal, implying that they all steal when they get past their early childhood. Once the prospector delivers his central claim, the reason for the competing understatements and overstatements becomes more clear - he has set the stage for the suggestion that parents should sell their babies as food when they are one year old. This outlandish statement will not be taken seriously because of the preceding juxtaposition between overstatement and understatement, and the reader will look past the initial outrage at the thought of selling babies as a commodity to the underlying meaning of the argument.
As he develops the argument, the prospector lists a number of problems he believes have contributed to the miseries of the poor in Ireland, blaming everyone from the English absentee landlords to the careless Irish themselves. The prospector eventually suggests that the English shouldn’t be troubled by eating the Irish babies since they have already "devoured" their parents. This harsh instance of irony relates to the idea that the unfair practices of the English landlords are hurting the Irish and keeping them from being productive.
After a thorough mix of appeals to logic and to emotion, the prospector ends his proposal with an appeal to ethics as he states he has nothing to gain from the proposal itself since he has no children to sell. Swift, in his brilliant satire, effectively manipulates rhetorical strategies and devices in order to show that the ironic solution is not nearly as inhumane as the poverty itself.