How we cite our quotes: (Chapter.Paragraph)
Quote #7
The only mystification in this was the imposing time of life that her elders spoke of as youth. (X.16)
Here, Maisie realizes that she doesn't understand what "youth" means since she hears adults use it to speak of one another as well as of young people like Maisie herself. This is a touching example of the way James communicates what Maisie knew by highlighting the limits of what her young mind can know.
Quote #8
Her reflexions indeed at this moment thickened apace, and one of them made her sure that her governess had conversations, private, earnest and not infrequent, with her denounced stepfather. She perceived in the light of a second episode that something beyond her knowledge had taken place in the house. (XI.4)
Maisie's youth keeps her from understanding everything that is going on around her, but it doesn't stop her from knowing that something is going on. This is James's way of showing us that children lack knowledge, but they don't lack intelligence. Maisie is whip-smart.
Quote #9
It was while this absence lasted that our young lady finally discovered what had happened in the house to be that her mother was no longer in love. (XI.4)
"Our young lady" is neither too young nor too ladylike to understand that her mom is no longer in love. James doesn't think that innocence (which Maisie certainly has) means that it's impossible to be observant and recognize the presence or absence of emotion.