Chapter 39 of Great Expectations is an example of Charles Dickens at his best. Characteristically, Dickens sets the stage for what is to happen by creating an appropriate mood:
It was wretched weather; stormy and wet, stormy and wet; mud, mud, mud, deep in all the streets. Day after day, a vast heavy veil had been driving over London from the East, and it drove still, as if in the East there were an Eternity of Cloud and wind. . . . Occasionally, the smoke came rolling down the chimney as though it could not bear to go out into such a night. . . .
Pip has become the English gentleman he aspired to be. He does not have to work for a living. He does not have to go out into the storm but can sit in a comfortable chair before the fire wrapped in a fashionable robe. When Magwitch appears at the bottom of the stairs, Pip receives him with cold politeness and shows the sang froid he has acquired by asking:
"Will you drink something before you go?"
Magwitch appreciates that line. It shows that Pip has indeed become a cold, snobbish, supercilious English gentleman. Then Magwitch takes malicious pleasure in making Pip realize that he is nothing but the creation of a wretched convict who was transported to Australia. Pip's world, including his own self-image, is shattered. He is horrified.
Pip had been living under the totally erroneous assumption that all the money he had received was coming from Miss Havisham, and that her motive was to turn him into an educated gentleman so that he could marry Estella and share a life of leisure and refinement with the girl he had adored since childhood.
This chapter is splendid because the reader is just as unprepared for Magwitch's reappearance and shocking revelations as is Pip himself. The covert message of this chapter is that the leisure class in general can enjoy its luxuries and indolence because of the toil, suffering, and privations of the people at the bottom of the social ladder. Poor Magwitch does not understand this truth because he is illiterate. He admires gentlemen and ladies with their carriages, beautiful clothes and refined manners without realizing that they are parasites who prey on people like himself.
Pip rather fastidiously believes that he can no longer accept money from Magwitch, even though the fugitive convict earned the money by honest hard work in Australia. Without the money Pip can no longer be a gentleman and can no longer hope to marry Estella. In subsequent chapters he goes to see Mr. Jaggers and Miss Havisham to reproach them for misleading him. These are wonderful scenes. Both these cunning, calculating, and devious characters deny that they even misled Pip and tell him that he created his own false illusions, his own "great expectations," out of his hopes and fantasies.
Dickens is saying that, generally speaking, it is not the selfish, arrogant rich people who will help you in this world but the hard-working and heavily burdened poor people like Joe Gargary and Abel Magwitch. This is in keeping with the message of Christianity in the New Testament, and this is the social message that inspires most of Dickens' works. He does not have any conspicuous political agenda. It is self-evident that the real world is built on and maintained by hard toil and that the people who don't work must be supported by the people who do.
Pip is sadder but wiser at the end of the novel, largely because of the information he receives from his secret patron Abel Magwitch.