And when you asked, as all history classes ask, as all history classes should ask, What is the point of history? Why history? ... But your "why?" gives the answer. Your demand for explanation provides an explanation. Isn't this seeking of reasons itself inevitably a historical process, since it must always work backwards from what came after to what came before?
Two related themes join this passage from Waterland to portions of Great Expectations. The interrelatedness of past, present, and future, stated clearly in the excerpt, assumes an integral part in the explanations for his life that Pip arrives at when he ponders Estella's history, which is in turn intertwined with the histories of Magwitch, Miss Havisham, and many others. Also, both authors emphasize the importance of curiousity (the questing process) as a way to impose logic upon the present -- Swift asserts that "the demand for explanation provides explanation," and Dickens shows that Pip, in trying to become a gentleman, finds out in the only way possible what a gentleman really is.
In terms of technique, both authors use foreshadowing to good advantage. The emphasis placed upon the question "why?" foreshadows the importance the question has for keeping Tom Crick sane. In Great Expectations, foreshadowing can be found everywhere -- in the deja vu feeling Pip gets in watching Estella wave goodbye (because Pip has seen the same features in Estella's mother Molly), in the way Pip keeps seeing faces in fire (forge fire, hearth fire, and then Miss Havishham literally on fire), and in many other places.