"The real evils of Emma's situation were the power of having rather too much her own way, and a disposition to think a little too well of herself; these were disadvantages which threatened to alloy her many enjoyments. The danger, however, was at present so unperceived, that they did not by any means rank as misfortunes with her." (1)
If the opening sentence is filled with resonant and charged words, this paragraph has one that jumps out at me: "evils." In a paragraph and indeed a novel that tends towards descriptors such as "misfortunes," "alloy her many enjoyments," and "disadvantages," the word "evils" stands in stark contrast.
One way we can approach this paragraph is to look at it as helping to solidify the distinction between Emma's thoughts and sensibilities and those of the narrator. It's hard to miss the point. The use of the word "real" to modify evils creates a necessary object of contrast--the "unreal" or imagined evils.
It is interesting to note that when thinking about the realm of power, the narrator insists that the power to have one's own way is a "disadvantage."
One significance of the word "evils" is that it practically forces the reader to approach the themes of the book, the conflicts and questions it depicts and raises, from a moral rather than (merely) ethical perspective. It is one thing to talk about getting your one's way as something that creates difficulties for a person within a particular social context; it is quite another to talk about it as something that disadvantages a person and is, hence, evil.
How, precisely, is Emma disadvantaged by having too much her own way? Or, maybe the better question might be: disadvantages in what? The only conceivable answer I can come up with is "character formation"-- and the assumption that having within one's power to have one's own way is a disadvantage pretty much carries with it the baseline assumptions that one's own will is corrupt and/or fallen and that the way to form character is through the experience of self-denial and/or submission.
These assumptions are generally prevalent (though sometimes more or less explicitly stated) in various systems of thought that advocated women's subordination. Is the narrator a complemantarian, then? It's probably important to point out that the word "evil," while applied to Emma's situation in this instance, is much harder to gender than some other words that would imply Emma's situation would be fine for a man. I'm also convinced that--harkening back to the word "unite" in the first paragraph, that Emma's problems are the combination of several things rather than the fault of any one attribute or mistake. Just as it is the uniting (or appearance of it) of the best blessings that sets Emma apart from those who are only handsome, clever, or rich, so too it is the combination of having her own way and thinking too highly of herself that places Emma in danger.
This explanation might go some ways to explaining why someone such as Knightley can wield power without it being to his detriment (and hence evil). He has somehow managed to avoid thinking too highly of himself in spite of the fact that he is practically perfect in every way. (Knightley's relative flatness in comparison to Darcy's more prickly and nuanced characterization probably goes a long way towards explaining the consistently greater popularity of Pride and Prejudice over Emma. Certainly he is Emma's superior in manners, sense, and [perhaps] morality, but her character is so much more richly and fully revealed to us over the course of the novel that it is hard for us to delight in the match as much as Emma does.)
Like so much in the novel, the simplest explanations of this passage are undercut or complicated by Emma herself. In the next two paragraphs we are told that Emma has exercised "self-denying, generous friendship" in promoting the match. Yes, this is Emma congratulating herself on matchmaking and patting herself on the back for being a good friend. And yes, the narrator is laughing and allowing us to laugh at Emma for taking credit for things she may not have been responsible for--in this case the match. Is no credit due to Emma here, though? Whatever joys she may feel in predicting the match, Emma would have to know that the culmination of such an exercise would be in some personal pain or disappointment as her friend moves on to another life stage and, necessarily, a lesser level of intimacy with Emma. Emma's action here foreshadow's her treatment of Harriet in book three, and it shows that however evil it might be to have too much one's own way, Emma is capable of putting others before herself to a degree often missing in adolescents of "nearly twenty-one years" who have labored under strict discipline all their lives.
Part of what I'm suggesting here is that Emma gets the brunt of a double standard. When she fails, she is the spoiled brat. But when she exercises virtue, she is often complimented for it in backhanded or reserved ways. She is called amiable and described as having a cheerful disposition as though such qualities--particularly in the face of sacrifice or suffering--were negligible or easy to come by.