Why does Pip have such conflicting emotions about Magwitch when he comes back into his life (Pip goes from disdain to sympathetic toward him)?
The most general reason for Pip's inconsistent feelings for Magwitch (Provis) is his lack of knowledge when it comes to the truth--his naivety. When Magwitch first shows up at Pip's apartment after so many years, Pip treats him much in the same way as he treats Joe after he is on route to becoming a gentleman--snobbily. Pip thinks that in order to be considered high class and sophisticated that he must distance himself from those who do not live up to high society's standards (namely for him, Estella's standards). However, all of these actions on Pip's part occur because he is naive, a poor judge of someone's true character, and because he does not have complete knowledge of all the influences in his life. Pip mistakenly thinks that Miss Havisham is his benefactress and sees Magwitch simply as someone to get rid of as quickly as possible.
When Pip begins to mature, in part because of Biddy's and Mr. Wemmick's influence, he opens his eyes to what is really going on. He discovers Magwitch's sad history; he finds out from Biddy how badly he hurt Joe when Joe came to visit him, and he realizes how manipulative and self-serving Miss Havisham and Mr. Jaggers are. Thus, when he sees everyone for who he or she really is, he adjusts his emotions toward each character, including Magwitch to what they should be.