What makes a character feel real? I've been asking this question for years and I've gotten no further than this: real characters have a relationship to the world that exceeds the plot. They want things the plot doesn't know about. They have opinions on things that don't come up. They feel the absence of what they've lost.

Isabel Archer in The Portrait of a Lady is real because her intelligence exceeds the narrative's use of it. She sees things clearly that she can't act on. Her choices are wrong in ways she partially understands. The gap between what she perceives and what she's able to do with the perception is the tragedy.

I'm suspicious of characters who want exactly what the plot provides them an opportunity to want. Real people want things at wrong times. Real characters should too.