The tone of the narrator in Jonathan Swift's "A Modest Proposal" (1729) is satyrical with a great degree of cynicism.
He also speaks with a humble and reasonable tone to present his ideas as legitimate in order to highlight the ludicrousness of serving children as food and cattle and that it could be taken as a serious solution to the devastating situation in Ireland. This tone can be seen already in the title "A Modest Proposal". These "reasonable" tone satirizes discourses that judge people in practical and economic terms. For example, he mentions that boys and girls are not a "saleable commodity", or later in the essay he states that "For this kind of commodity will not bear exportation, the flesh being of too tender a consistence to admit a long continuance in salt, although perhaps I could name a country which would be glad to eat up our whole nation without it."
The tone allows him to effectively satirize people who turn humanity into cold economic thought. On a logical level, the argument is flawless, but it is morally abject. It is important to bear in mind that the essay was first published anonymously. By hidding Swift's authorship, the readers did not know it was the work of the famous satirist, so it had a more powerful effect without looking for the joke from the beginning.