The first view we have of Jill Pole is not very favorable: She's crying behind the gym of her school, awaiting a beating from a group of bullies who rule the place. Jill feels sorry for herself and snaps at Eustace Scrubb, a classmate who understands what it means to be tortured by these louts.
So why does Lewis open The Silver Chair by focusing on such an unpleasant child? For one thing, most of us can empathize with Jill. Who hasn't been stuck at a school they've hated, with people who are overbearing or downright dangerous? Jill's vulnerability and our sense of shared experience with her as readers make her a very attractive character indeed, especially for the school-age set.
Jill is also wide open to possibility and imagination, something that the usual inmates of Experiment House seriously lack. When Eustace tentatively reaches out to share the cherished secret of his adventures in Narnia with her, she gives the best possible answer:
"Pole, I say, are you good at believing things? I mean things that everyone here would laugh at?"
"I've never had the chance," said Jill, "but I think I would be." (1.6-7)
She gives truthful and humble-sounding response, which allows Eustace to share what he knows about Aslan and call out to him. In other words, it's Jill's willingness to believe that makes the adventure in Narnia possible.
It's hard to imagine that Jill and Eustace are only around ten years old at the time of The Silver Chair. They've already learned to be careful with each other's feelings in difficult moments and to look out for each other (note how they hold hands when jumping through the door in the wall and entering Aslan's mountain). Both Jill and Eustace seem so capable.
But first impressions can sometimes be a little deceptive. Jill is, after all, only ten, so we kind of know that it won't be long before the mature façade breaks down (don't forget, when we first meet her, she's crying). And it does, spectacularly, on the edge of the highest cliff ever known to man or beast.
When Jill sees weakness in Eustace and understands for the first time that she is superior to him in something, she relishes that power and feels hatred for her friend's weakness. It's an unworthy feeling that she later repents, but in the moment, she can't control her impulse to push her friend to the edge of his fears:
She didn't mind in the least standing on the edge of a precipice. She was rather annoyed with Scrubb for pulling her back—"just as if I was a kid," she said—and she wrenched her hand out of his. When she saw how very white he had turned, she despised him. (1.15)
This is not a great moment for our little heroine, but the experience in Narnia is meant to prepare the characters to be nobler, kinder, and certainly more just and honest with themselves than they have been before. Jill learns, when she comes face-to-face with Aslan, that there will be no way to avoid her shortcomings or to fob them off onto Eustace.
That lesson takes a long while to sink in, for both Jill and Eustace. While Jill has some first-rate qualities necessary for a fantasy protagonist, she also has a lot to learn. And she has to play catch-up with Eustace, who has been on adventures in Narnia and benefits from a return of strength and courage gained in the past, which decidedly does not improve her temperament. Nor do the trials that they have to face on the road to the lost prince.
In fact, Jill throws her fair share of tantrums on the road—some nearly sacrilegious in nature (since Aslan's kind of a stand-in for Jesus, but more on that elsewhere in this section)—often because she recognizes her own shortcomings and can hardly bear it:
[…] deep down inside her, she was already annoyed with herself for not knowing the Lion's lesson quite so well as she felt she ought to have known it. This annoyance, added to the misery of being very cold and tired, made her say, "Bother the signs." She didn't perhaps quite mean it. (7.101)
After reaching this crisis point, and with a little help from her friends, Jill learns that she has to own her mistakes and take on the responsibility for righting them. It's a big lesson for a young person to process, but when Jill turns the corner on this one, she's so very much closer to being the person that Aslan expects her to be.
By the time the crew faces their final and most fraught trial—releasing the Knight/Prince from the silver chair—Jill is the first one prepared to do the right thing. She accepts what must be done and urges Puddleglum and Eustace on, telling them, "'Let's get it over. Good-bye, everyone" (11.167). She is not certain how things will unfold from here, but she is certain that freeing the man is the right thing to do—it's what Aslan would want, after all—and so she steps up and leads the charge to get 'er done.
Kids hate being reminded how small (and therefore unimportant) they are, and Jill has the double whammy of also being a girl in a boy's world. For Jill, these realities collide most irritatingly when she meets the Black Knight for the first time and calls him out (quite rightly) for planning to be a tyrant:
"What?" said the Black Knight, still laughing and patting her head in a quite infuriating fashion. "Is our little maid a deep politician? But never fear, sweetheart…" (11.59)
We don't even need to continue his speech here—you get the picture. On the positive side, at least Lewis recognizes how horrible the Black Knight is being here and sympathizes with Jill's anger.
Part of Jill's challenge in Narnia, then, is not simply overcoming her personal flaws or learning to travel in the worst possible conditions. She has to face up to the fact that she's the only girl on this mission. It means that Puddleglum and Eustace get both swords and bows to carry—for protection and hunting—and Jill gets to carry the eels and biscuit. For real.
When she attempts to protest, she's cut short by Puddleglum's comment that they're killing each other already. While Jill wants an equal share in the adventure, she doesn't want to be the cause of trouble or failure of it, so she sticks with her girl scout knife and tries to be contented with her lot.
Writers like Neil Gaiman and J.K. Rowling have commented on the anti-feminism they see in the Chronicles, particularly in the character of Susan (Eustace Scrubb's older cousin), who is not allowed to return to Narnia after the first adventure.
Rowling believes that Susan is barred because she has grown into a young woman and is somehow not tough enough to make the cut. While Jill is still quite young and certainly a central character for The Silver Chair, there is a kind of uneasiness with her role in the work. She's good at things—like working with horses—but her truly shining moment happens when she plays the little coquette at Harfang to get full access to the house:
The others admitted afterward that Jill had been wonderful that day... she had began making a tour of the whole castle and asking questions, but all in such an innocent, babyish way that no one could suspect her of any secret design […] She made love to everyone—the grooms, the porters, the housemaids, the ladies-in-waiting, and the elderly giant lords whose hunting days were past. She submitted to being kissed and pawed about by any number of giantesses […]. (9.126)
Jill's primary value here is as a doll, using her girlish wiles to get on the good side of the giants to find access to an exterior door. She is "babyish" and wooing everyone with her charms, allowing them to kiss and touch her as they please—in other words, she is revered for her ability to both make people adore her and revealed to readers as being capable of being pretty slick and tricky. And, of course, a key part of Jill's ability to pull this whole deceit off lies in not drawing lines around her own body and who can access it.
So while there is no doubt that Jill is a protagonist in this story and fulfills the journey to the best of her ability, there's still a sense that she doesn't necessarily get to do it the way she might have liked. We know this because her goal in all the action scenes is not to "faint—or blub—or do anything idiotic" (13.185). She is always trying not to be herself to some degree in order to survive. But then, like we see in the excerpt above, she's also presented as sort of sneaky for doing this. And all the while, her cohorts think she's wonderful for busting out her lady skills.
Whatever Lewis' view of Jill, we know that she proves her courage by overcoming fears (the whole Aslan thing and squeezing into dark places underground), learns to take responsibility for her mistakes, and becomes a true friend to Eustace and Puddleglum. And she doesn't even die on the journey. That's a lot for one ten-year-old in an adventure.