Ironically, Pip believes that if he truly relates what occurred at Satis House, he sister will think it too fantastic a tale to be given credibility. So, he edits the appearance of the inhabitants and the house and the actions that have occurred. In addition to feeling that no one will understand Miss Havisham, Pip also feels that there is something "coarse and treacherous" about his revealing the truth of her character and appearance. Interestingly, in this sentiment there is also irony as Pip reveals that he is of a noble character although he perceives Estella and Miss Havisham as superior to him.
Added to the convictions of Pip regarding his report of his visit to Satis House is his repulsion of the preposter, Uncle Pumblechook who hurries to Joe's house to learn the news.
And the mere sight of the torment with his fishy eyes and mouth open, his sandy hair inquisitively on end, and his waistcoast heaving with arithmetic, made me vicious in my reticence.
While Pip fabricates an elaborate story about what he has seen and done, he does tell the truth about the house being lit with only candles, for he realizes that Pumblechook is aware of this fact although he knows nothing of the inside of the house since he must wait outside whenever he does business there.
Later, however, Pip confesses to Joe that he has lied and that he feels very miserable because Estella has made him feel common. In fatherly fashion, Joe instructs Pip that "lies is lies." But, he tells Pip, lying is no way to get out of being common; besides, Pip is "uncommon in some things," he lovingly comforts Pip.