Middlemarch is, as we learn from the subtitle, a "Study of Provincial Life." Sounds scientific, doesn't it? And science calls for objectivity. It's important for the narrator to look at the characters and events she's describing as though they're samples under a microscope. Most of the time, she maintains a level of scientific detachment. Sometimes, though, she breaks out of that tone and becomes more sympathetic, like when she says, "For my part I am very sorry for him" (3.29.3). This sympathy for Casaubon is quite a switch from earlier, when the narrator describes the "strong [microscopic] lens applied to Mrs Cadwallader's matchmaking" (1.6.71).