The overriding logical fallacy in Jonathan Swift's satirical essay "A Modest Proposal" is Appeal to Authority in which the speaker sets himself up as logical and rational and an expert on the condition in Ireland, even citing the specifics of what the children do when they grow up. In keeping with the satire, the third paragraph reveals the speaker to be slightly crazed, or rather, one who has carried reason, logic and calculation to a gross extreme that is the inversion of reason and logical decency. Another logical fallacy employed is Two Wrongs Make a Right whereby the speaker addresses the wrong of poverty and childhood starvation with the wrong of developing a childhood commodities market similar to the Pork Bellies Commodity market.
Jonathan Swift's "A Modest Proposal" is a brilliant example of satire from one of the undisputed masters of the craft, and it's primary logical fallacy is an Appeal to Authority. Essentially, Swift's narrator sets himself up to seem knowledgable, reasonable, and generally wise, before descending into a loony discourse on the benefits of devouring Irish children. The importance of this fallacy becomes especially funny (and, it must be noted, bitter) once one takes into account the context in which it occurred.
The "Proposal" was by no means Swift's first political pamphlet. When he published it in 1729, he had already written several political essays. In 1720, for instance, Swift wrote "A Proposal for Universal Use of Irish Manufacture," an argument for the use of Irish goods to improve the Irish economy. Then, in 1724, Swift wrote the "Drapier's Letters," a series of attacks against a potentially disastrous economic scheme that threatened to render an already impoverished Ireland still poorer. Although he wrote under a pen name in these writings, Swift approached them earnestly, offering sound and sage advice regarding the avoidance of the impending economic crisis. Though both pamphlets offer reasonable and easy to follow advice, Swifts ideas were generally ignored, and he watched with growing frustration as Ireland continued to stagnate.
Viewed with this context in mind, it is possible to assume that the "Proposal's" fallacious Appeal to Authority is a critique of the general populace. They wouldn't listen to Swift's previously sound advice, so he would respond by offering the advice of a lunatic. Thus, the crazy devolution of the pamphlet's argument is not only a satirical example of a logical fallacy; it is also a criticism of the lack of logical reasoning used to govern Swift's country.
Two major fallacies are in evidence throughout the masterful and enduringly relevant text of "A Modest Proposal." The first and most immediately obvious is the appeal to authority. The author-in-character consciously adopts a tone of paternalistic knowingness, setting himself up as an authority with no real grounds to do so by quoting unsubstantiated statistics:
The number of Souls in this Kingdom being usually reckoned one Million and a half, Of these I calculate there may be about two hundred thousand Couple whose Wives are breeders, from which number I Subtract thirty Thousand Couples, who are able to maintain their own Children... I again Subtract fifty Thousand for those Women who miscarry, or whose Children dye by accident, or disease within the Year...
The reader is given no assurance as to the source or accuracy of these statistics, since their purpose is to give an effect of authority, rather than to encourage rational analysis. The fallacious appeal to authority is furthered and augmented by quoting an unnamed "very worthy Person, a true Lover of his Country, and whose Virtues I highly esteem," adding the non-sequitur to the parade of fallacies Swift intends to expose (what does the author's opinion matter?). A further authority quoted, "the famous Sallmanaazor, a Native of the Island Formosa," is actually fictitious, further highlighting the absurdity of continually deferring to absent authorities when rational justification is lacking.
A second fallacy that pervades "A Modest Proposal" is the appeal to emotion, which is pursued in several forms. The vivid depiction of poverty in the early paragraphs is intended to provoke an emotional response that will make any proposal desirable, if only it will diminish the spectacle of such suffering. Such appeal is most pronounced in the following paragraph:
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.
Here the author-in-character relies on the pity, shame and disgust provoked in his readers, rather than the strictures of reason and justice, to render his proposal more palatable. The shame that appears here as elsewhere is linked to patriotism, with references to "the present deplorable state of the Kingdom," "a true Lover of his Country," and to bigotry in the form of religious hatred, revealed in the pointed reference to "lessening the number of Papists among us."