"She knew that what Marianne and her mother conjectured one moment, they believed the next—that with them, to wish was to hope, and to hope was to expect."I've known people like that, men as well as women.
"She" in this case is Elinor Dashwood. There is no character in literature I identify with quite as much as I do with Elinor. Not that I lived up to her standards. It is more of an aspirational thing than a matter of commonality; I think I'm a lot like her but not so much as I should be.
The issue here is exactly what the title of the novel would have us suspect: sense and sensibility. Elinor is a perfect balance of both. That, I believe, is the key to understanding this novel. The key moment of Pride and Prejudice is the one where Elizabeth says, "Till this moment, I never knew myself." I had a moment like that myself this year. But that sort of moment could never happen with Elinor. Elinor already knows herself.
If we have a look at the full quote from Pride and Prejudice, we can see it all clearly.
"How despicably have I acted!'' she cried.—"I, who have prided myself on my discernment! — I, who have valued myself on my abilities! who have often disdained the generous candour of my sister, and gratified my vanity, in useless or blameable distrust.—How humiliating is this discovery!—Yet, how just a humiliation!—Had I been in love, I could not have been more wretchedly blind. But vanity, not love, has been my folly.— Pleased with the preference of one, and offended by the neglect of the other, on the very beginning of our acquaintance, I have courted prepossession and ignorance, and driven reason away, where either were concerned. Till this moment, I never knew myself.''Elinor would never court prepossession and ignorance and drive reason away. Her sister Marianne, on the other hand, could easily do so. And does.
Exactly how she does so is what we see in the quote at the top. From conjecture to belief, what does that mean? The explanation comes after the dash in three progressive emotions: wish becomes hoping and hoping becomes expectation. But how?
Well, I know how I'd explain it. I'd go with Robert Solomon's argument that each emotion embodies a judgment. There is the judgment that leads to the emotion. Wishing is based on a judgment about facts. We always wish for something. But there is a second judgment that follows. We become aware that feel an emotion and that ought to imply a further judgment.
It won't lead to a further judgment unless we train ourselves to make it. There are natural progressions to emotions and Elinor, for we are surely in her head here, has diagnosed one accurately. I say progressions for they don't inevitably lead the way they do here. I've known people who go from wishing to resignation. The point is that it's an habitual way of proceeding. Elinor knows because she has seen it many times before. Marianne and her mother don't know because they don't have "sense".
"Sense" cannot, and does not, mean rationality here. All three of these women are equally rational. They are, in fact, equal in both rationality and feeling. Sense is something else. I have some notions of what that might be but I'm withholding judgment for now. That is, after all, what Elinor would do.