Abbott seems to have something to say about culture and society in his own world of four dimensions and is getting it said via Square’s description of Flatland:
Rarely–in proportion to the vast numbers of Isoceles births–is a genuine and certifiable Equal-Sided Triangle produced from Isoceles parents. Such a birth requires, as its antecedents, not only a series of carefully arranged intermarriages, but also a long, continued exercise of frugality and self-control on the part of the would-be ancestors of the coming Equilateral, and a patient, systematic, and continuous development of the Isoceles intellect through many generations. (p. 8)
Flatland’s strict social structure reminds me of Margaret Atwood’s The Handmaid’s Tale, wherein the status is determined by the occupation of the individual, though the explanation above obviously indicates that all stations have breeding rights, which Atwood’s world did not allow. However, while the inhabitants of Flatland are also known by their geometric form, Atwood’s characters were distinguished from one another by their attire, both in color and style. But we can see how a jig or jag in a gene in a Triangle can produce a Square–and this child would become a higher form, but wait, here’s what happens:
The birth of a True Equilateral Triangle from Isoceles parents is the subject of rejoicing in our country or many furlongs around. After a strict examination conducted by the Sanitary and Social Board, the infant, if certified as Regular, is then immediately taken from his proud yet sorrowing parents and adopted by some childless Equilateral (…)
There then is the similarity to Atwood’s future world. Not only is social strata of prime importance, there’s the acceptance of this outrageous behavior for another reason, one that existed and likely will always exist as a large part of man’s nature, that of the grumbling of inequality and eventual war. The upper classes of Flatland understand that the lower classes, with this one hope of bettering themselves in generations to come, were less likely to rebel.