What are rhetorical devices in a modest proposal?

Rhetoric is the art of persuasion. It helps a speaker/writer sway an audience in his/her favour. Jonathan Swift uses satire and irony in this work, yes, but the very heart of these two terms are founded on the original (Greek) areas of persuasion. There are three main rhetorical devices used in literature, and these are employed (masterfully) by Swift in his "A Modest Proposal."

Logos -- Does an argument or statement appeal to the audience's capacity for reason, logic, or sensibility? Can you trust the speaker's use of logic?

I.e: Will cannibalism actually benefit the masses or the economy?

Ethos -- Is an argument ethical? Does it adhere to the socially accepted norms or propriety, or decency? Can you trust a speaker's motives?

I.e: Is it better for children to starve to death, or for them to be slaughtered in early life? Which is more acceptable?

Pathos -- Does an argument appeal to you, the speaker? Does it strike a chord with you, does it evoke any emotional response, and how so?

I.e: Can we sleep at night if this "modest" proposal becomes a norm?

As mentioned above, these three devices are always at play with satire and irony; they are the "backbone" of both these terms.

Remember: Irony: when the intended meaning of a statement is OPPOSITE of the words used. This also can be called sarcasm. I.e: "I REALLY like that shirt (not). Or, England is sucking us dry, we might as well beat them at their own game, (Which is the satirical message of "A Modest Proposal." Swift was not literally suggesting cannibalism, but he was using this narrative to illustrate just how England was figuratively consuming all the assets in Ireland).