Her hair is so faint and pale a brown—not flaxen, and yet almost as light; not golden, and yet almost as glossy—that it nearly melts, here and there, into the shadow of the hat. (22.214.171.124)
This image of Laura practically melting is crucial to understanding her character, or lack thereof. Laura is a bit like a shadow, a blank slate of a romantic lead who's never very well defined. You can read more about Laura's lack of definition in her character guide.
Think of her as you thought of the first woman who quickened the pulses within you that the rest of her sex had no art to stir. (126.96.36.199)
Here's further proof of Laura's blank-slatehood in this line from Walter. Walter basically tells readers to superimpose their own ideal woman onto Laura, making her a sort of everywoman heroine… and sex symbol.
"I see it—more unwillingly than I can say. To associate that forlorn, friendless, lost woman, even by accidental likeness only, with Miss Fairlie, seems like casting a shadow on the future of the bright creature who stands looking at us now." (188.8.131.52)
Anne and Laura's close ties are at the core of the book's identity theme. At first glance Anne seems like a negative image, or the opposite of Laura. But Anne herself has some positive qualities (such as a willingness to act) that the super-passive Laura lacks.
If ever sorrow and suffering set their profaning marks on the youth and beauty of Miss Fairlie's face, then, and then only, Anne Catherick and she would be the twin-sisters of chance resemblance, the living reflexions of one another. (184.108.40.206)
This idea of a "twin-sister of chance resemblance" and the concept of "living reflections" pretty much sums up the book's identity theme. Identity isn't very stable in this book, and reversals, doppelgängers, and chance can alter it.
But resolute, clear-minded Miss Halcombe, was the very last person in the world whom I should have expected to find shrinking from the expression of an opinion of her own. (220.127.116.11)
Mr. Gilmore introduces an interesting question here—whether or not you can ever really know another person and predict how they will behave. In the world of The Woman in White, the answer is "Nope. Everyone is mysterious."
He could only assume that the intensity of Miss Halcombe's suffering under the loss of her sister had misled her judgment in a most deplorable manner; and he wrote her word that the shocking suspicion to which she had alluded in his presence was, in his opinion, destitute of the smallest fragment of foundation in truth. (18.104.22.168)
Laura's loss of identity has pretty widespread effects. Walter and Marian are altered by their connection to Laura, and the rest of the world pretty much thinks they're nuts. The diction here is worth noting: lots of big words and almost legal lingo, which is Walter's way of dealing with an emotional situation.
"Questions of identity, where instances of personal resemblance are concerned, are, in themselves, the hardest of all questions to settle." (22.214.171.124)
Words of wisdom from Mr. Kyrle. Even in the eyes of the law, identity isn't necessarily absolute, which was a scary thought for the Victorians.
The idea that he was not Sir Percival Glyde at all, that he had no more claim to the baronetcy and to Blackwater Park than the poorest labourer who worked on the estate, had never occurred to my mind. (126.96.36.199)
Sir Percival not really being Sir Percival kind of blew our minds, too. We (like the Victorians) are trained to take people on their word, and are rattled when people are (dun dun dun) not what they appear to be.
"I beg your pardon, Sir Percival—" he began.
I stopped him before he could say more.
"The darkness misleads you," I said. "I am not Sir Percival."
The man drew back directly.
"I thought it was my master," he muttered in a confused, doubtful way. (188.8.131.52-5)
In one of the coolest scenes in the novel, a servant mistakes Walter for Sir Percival. It's like a thematic anvil to the head. Mistaken identity! Foils! Freaky connections! By being mistaken for one another Sir Percival and Walter are being compared to Anne and Laura.
"The only danger," I replied, "is that Sir Percival Glyde may have been recalled to London by the news of Laura's escape. You are aware that he had me watched before I left England; and that he probably knows me by sight, although I don't know him?" (184.108.40.206)
Sight and recognition are a crucial part of the book's identity theme. The idea that Sir Percival may know Walter but that Walter doesn't know Sir Percival is all sorts of terrifying: recognition is, as this quote expresses, power.
"For the last time I say it—on my honour as a gentleman, on my oath as a Christian, if the man you pointed out at the Opera knows me, he is so altered, or so disguised, that I do not know him." (220.127.116.11)
Time alters nearly every character in this novel—people suffer from illness (Marian), eating too many pastries (Fosco), trips to South America (Walter), and stays in asylums (Laura). Physical alterations become downright commonplace, but the real trick is determining whether physical changes alter people's inner selves. How does identity change over time?