One of James' contributions to the art of fiction is in his use of point-of-view. By point-of-view is meant the angle from which the story is told. For example, previous to James' novel, much of the fiction of the day was being written from the author's viewpoint, that is, the author was telling the story and he was directing the reader's response to the story. Much of the fiction of the nineteenth century had the author as the storyteller, and the author would create scenes in which certain characters would be involved, but each scene would not necessarily have the same characters in them.
James' fiction differs in his treatment of point-of-view. He was interested in establishing a central person about whom the story revolved. Usually, the reader would have to see all the action of the story through this character's eyes. This central character was called at times the "central intelligence" and at times the "sentient center." Thus in James' fiction, we have the central character of the novel, and it is as though the central character were telling the story because we see or hear about all events through him. We the readers react to certain events as this central character would react to them.
Every scene in the novel, therefore, will be a scene which reveals something about the main character, and usually he is present in every scene. As the central intelligence, his sensibility is the dominant aspect of the novel. In The Portrait of a Lady, Isabel Archer is, of course, the central character. Every scene is limited to showing her involved in some type of situation, and every scene confines itself to the interests of this central character.