In Chapter 19, as Pip prepares to leave for London to become a gentleman, he has a favor to ask of Biddy.  He wants her to teach Joe manners so that when he is in a position to do so, he can move Joe in with him and supposedly "save" him from his lot in life. He tells Biddy that Joe's current manners will "hardly do him justice" in London's high society.  Biddy's response is,

"And don't you think he knows that?" (165).

Pip is surprised by Biddy's question.  He assumes that because Joe is so easy-going and seemingly ambivalent about social graces that he wouldn't even be cognizant of his "need" for etiquette lessons.  Biddy explains to Pip that Joe is too proud to ask for help and that he is comfortable and competent at the forge and would most likely desire to stay there.

Biddy is too tactful to tell Pip that she sees the truth behind his request.  Pip is ashamed of Joe and worries that Joe will embarrass him when he starts to make new high class friends and has established a reputation for himself.  It is doubtful that Pip even sees this about himself at this point in the novel because he not very self-aware.  Of course, Biddy is correct in her assumption, and Pip eventually does treat Joe very poorly when he comes to London.