First of all, what kind of a name is St. John Rivers? Who would name their kid St. John?
St. John is perhaps either John the Baptist (which would make a bit of sense, a martyr and an ascetic) or John from the gospels (the disciple Jesus loved). The first John, in considering the temperament of St. John Rivers, makes the most obvious sense. St. John Rivers has long been acknowledged as cold, calculating, exacting, ambitious, stoic, severe, etc, and does make himself and his passions martyrs to his religious zeal. On the other hand, we know he has a passionate side from his love for Rosamonde Oliver - albeit an unacknowledged and smothered passion. In this he might be more like the apostle John in a way - he does love. He can love passionately, but he consciously subdues his love to his greater love, which is sometimes difficult to dissect or understand. Does St. John love God with so much cold and fiery passion? Or is it really himself, his own pride of martyrdom, the kind of craze that drives some ascetics to starve themselves or live on top of pillars for years, the kind of passion that is really ambition, that is on the borderline of being pharisaical? I've read Jane Eyre many times over the years, and I still can't figure St. John out. Jane finds him frightening. I think he's fascinating.
And on the other hand, of course, we have Jane's choice, Mr. Rochester. Mr. Rochester is as equally brusque as St. John and as practical and unsparing of the feelings of others. He is also, we might argue, as prideful and ambitious. The main distinctions most people seem to make between Jane's two suitors is that St. John is holy, cold, and antiseptic while Rochester is a sinner, warm-hearted if tough. As he says of his own heart, it is like an India rubber ball that is very tough, but that can change back with the right encouragement. St. John, on the other hand, is inflexible, like steel.
Some critics that I have read have presented the difference between the two as the natural dichotomy of a religious tale - Heaven rejoices more for a repentant sinner than a peerless saint, so Jane, a missionary in her own right, chooses the sinner rather than the saint. Well, that makes sense in a way, I suppose.
There are other readings of it (more feminist readings) which see St. John as the more intractable husband - who will, as Jane herself admits, force her to hide half of her nature and expect her to be something she can't ever be - like himself - classically, dogmatically perfect. And though Rochester also begins as a dominator, because of her resistance and the circumstances of the novel, he becomes a tractable partner who Jane will lead rather than follow. And that reading makes sense too.
Dr. Menke's take on it is somewhat amusing. He says that most of these Victorian novels (even beginning as far back as Austen) operate under the stipulation that the real suitor is the one whom the heroine first rejects and then accepts only after deception or misunderstanding has been removed. I like that one, to some degree. Darcy, Rochester, Wentworth, Thorton, even Heathcliff (in a way) make their first proposals erroneously and only after it seems like the two characters will never get together do they end up clearing up the miscommunication (or obstacle) and reunite (even in death). It's a common plot of romances. I wonder which came first?
But about St. John and Rochester. Here's my take on it. I think that St. John and Rochester are really almost the same person, in a way, or the same kind of man. They are both severe and cold and rigid in their own ways; they both want and expect obedience and compliance. I think it's significant that Rochester tells Jane on that first night that he was once her equal, before life dissipated him. Her equal in goodness. I think St. John sees the same thing in Jane - her goodness. I won't say "niceness" because it doesn't really mean anything any more, and certainly not what it meant then. But, the funny thing is that Jane resists and rebels against both of them. She rejects both their proposals (neither a clear proposal of marriage - one is a invitation to adultery, and the other a business contract). She makes it clear that marriage has to have love and legitimacy. Form and content. She is good, but she isn't nice and she isn't exactly kind. She's often quite mean. For good reasons, but still. She isn't who they think she is - and she knows that.
"I'm no angel," she tells Mr. Rochester, and he shouldn't expect her to be. The same is similar of St. John; Jane knows she can't become a saint alongside him; she can't turn her green, changeable eyes blue (like his).
And what I also find fascinating is that Jane does not begin as the heroine we should expect St. John and Rochester to love (especially not for her goodness). If we wanted the promise of that we would look to Helen Burns. She is closer to being the "good angel" or the helpmate that the two men rhapsodize about. Not Jane.
Jane is a rebellious, sensitive, overly-imaginative, willful, vengeful kid. I like her for it. But I think only Rochester is capable of liking her for it too. St. John tends to get a bad rap, and I think he does have a great understanding, but I think even if he can acknowledge those attributes in Jane, her elfin side, he would already expect her to curb it (just as she's spent most of her life doing).
Jane's greatest strength is remaining true to herself by learning how to control herself. Rochester can't (or won't) control his feelings, and St. John has so much control that he daily murders his feelings. I think Jane is the stair step between them, rather than simply the spoke. Jane has the potential to become Rochester or St. John. She could give in to her passions as she did when she was younger (that was for justice's sake) and the even more powerful motivator of love is very convincing. But she doesn't. She can sacrifice. She already even has a bit of a taste for self-mortification. She and St. John could be a pretty pair of masochists. She could spend her life in achieving something she already knows is impossible. She's already skilled in self-deprivation.
But she doesn't. But the only reason she doesn't is because of a miracle. For Jane, the right answer is to go with St. John and become the next thing - to bury that passionate part of her once and for all and realize that she really is formed for labor, not love. It's only though a miracle that she doesn't go down this road.
I think it's interesting that The Eyre Affair capitalizes off of this very feature. I think it's significant that Jane has that part of her nature that responds to St. John's powers of persuasion. I think sometimes there is something in that idea of being utterly obliterated in something else that is almost irresistible.
That's why the end of Jane Eyre always puzzles me. Most people know "reader, I married him" but they don't remember that the book actually ends with St. John's last letter. It always has intrigued me on a personal level.
I think if I had been Jane, I probably would have gone with St. John. That influence, the idea of a half sacrifice being unworthy, would most likely have swayed me at one point in my life, and at this point, I would likely have left both of them. It seems they both want something Jane can't give either way.