A human being always acts and feels and performs in accordance with what he imagines to be true about himself and his environment...For imagination sets the goal ‘picture’ which our automatic mechanism works on. We act, or fail to act, not because of ‘will,’ as is so commonly believed, but because of imagination.
The characters who go to make up my stories and novels are not portraits. Characters I invent along with the story that carries them. Attached to them are what I've borrowed, perhaps unconsciously, bit by bit, of persons I have seen or noticed or remembered in the flesh - a cast of countenance here, a manner of walking there, that jumps to the visualizing mind when a story is under way. I don't write by invasion into the life of a real person: my own sense of privacy is too strong for that; and I also know instinctively that living people to whom you are close - those known to you in ways too deep, too overflowing, ever to be plumbed outside love - do not yield to, could never fit into, the demands of a story. Characters take on life sometimes by luck, but I suspect it is when you can write most entirely out of yourself, that a character becomes in its own right another human being on the page.