At first glance. Castle Rackrent is somewhat of a romp-come-fable that warns against the perils of wanton profligacy. Introducing the reader to one irresponsible Rackrent heir after another, the author manages to introduce us to a family with no aptitude whatsoever for fiscal responsibility, who get exponentially poorer generation after generation.
However, when we learn that this is the only book that Edgeworth wrote that was not first edited by her father, we are able to read the messages between the lines that she is subtly using to feature her own particular soap box issues within the novel. The key one of these is her support of co-ed schools. Edgeworth, considered quite progressive in her views on education, believed that boys and girls should be educated together and in the same way. This was far from the mainstream belief in her day, but a study of the relationship between the male and female characters in the book shows a certain tendency for the women to stride out on their own and in some cases come out on top. For example, Sir Kit's bride might have lost the battle, in terms of having the staff of the household respect her and her instructions, but she ultimately wins the war by cutting off all funding to her economically-challenged husband. Even Isabella, although forced to conform to her father's wishes by the end of the novel, is able to strike out on her own in an act of open defiance, leaving behind her family and her inheritance for the right to marry the man of her choice. This is also another frequent Edgeworth motif, as she believed that women should have the right to choose whom to marry and not be governed by societal or family expectations.
Edgeworth also believed firmly in the Act of Union of 1800 She realized that this might not be popular among her readership, particularly the Irish contingent, because the Act itself was not particularly popular in Ireland. The Irish believed that they should remain an independent nation whilst continuing to receive subsidies and benefits from the British Crown; England, on the other hand, believed that if subsidies were to continue then they have better come with a degree of commitment from the Irish, and passed the Act of Union that saw Ireland become the fourth nation to join the British Isles. Edgeworth firmly believed that this Act was a positive for both England and Ireland; although her heart remained firmly with the nation of her Celtic roots, she was savvy enough to recognize that productivity and financial ability were not among the traits of the average Irishman, and consequently believed that they would be better served by becoming part of the nations under the crown.
Another issue that the author was passionate about was religious freedom and equality. Although this was generally with regard to the England / Ireland Church of England versus Catholicism argument, she actually demonstrates the perils of religious discrimination in the book by showing the disrespectful way in which Sir Kit treated his wife when it came to her Jewish faith. Far from being a mere pastoral novel, with several ironically comical characters, this is a novel that presents several important political and sociological issues to the reader under the guise of writing a novel about financially incompetent Irish aristocrats.
