The concept of the unreliable narrator is an intriguing one in literature. The reliable narrator is one who is by and large rational, objective, unbiased and informative, in a straightforward way. The unreliable narrator, by contrast, can mislead the reader (whether intentionally or unintentionally), subvert the narrative, or take an approach to his/her material that is inappropriate or confusing. He or she might be altogether too subjective, allowing his/her judgement to be clouded by emotion or prejudices. This leads to the suppression or distorting of facts, events, information.
Sometimes the unreliability of a narrator can be quite blatant, at other times more subtle. In the case of A Modest Proposal, the narrator starts off in a deceptively restrained and dignified tone, quoting facts and statistics to support his case. He gives the overwhelming impression that he is taking quite a straightforward approach to his subject - until he reveals his shocking proposal that the children of poor Irish people should be fattened and sold for food, thus rendering them useful by cutting down on the suffering population and earning their parents money. Obviously, this is a premise that no sane reader could accept, and at this point it suddenly becomes obvious that the entire essay is couched in the most ironic manner imaginable.
In 'Shooting an Elephant', the narrator is also unreliable in letting his emotions cloud his perspective on his work as a colonial officer in British-run Burma. He detests the whole Imperialist system and this leads him to despise both colonisers (himself included) and the colonised. He describes the natives who make fun of him, in the most scathing terms, and in the end the only character to come off with any dignity in the piece is the elephant. This obscures the actuality of the situation that he describes; we as readers are not able to see these 'natives' for what they really are. Here, then, as in the Swiftian essay, we have an unreliable narrator, although in a different way.
The advantage of having a reliable narrator is obvious: the reader can generally trust his/her word, take what he or she says more or less at face-value and get an overall clear picture. With an unreliable narrator, though, the reader has to abandon this position of trust and work a little harder at developing understanding, reading between the lines, filling in gaps, forming judgements of his or her own.
On the other hand, an unreliable narrator may make for a more memorable piece overall. A Modest Proposal is undeniably an outstanding example of this. Rather than present a dry and detached argument about the evils of the Irish situation, the narrator utterly shocks us with his wholly unorthodox solution to the problem. This jolts us into a sharper, horrified understanding of the unalloyed misery of the Irish poor. It forces us to take note. In 'Shooting an Elephant,' meanwhile, while we might not get clear-headed statements about British Imperialism, we can see its effects on at least one young wretched colonial officer and come to appreciate the emotional complexities of the situation in this way.