The Character of Portraits

Some portraits seem to me to be about psychology and character. Yet the kind of portraits we're talking about are static. How can you represent something which relies on changes over time in a medium that doesn't move? This gets into the question of whether a person has an essence and some sort of characteristic way of presenting him or herself to the world. And so I do tend to defend a view like that. It's related to something that Roland Bart calls the heir in his book Kamara Lucida, the book that he did on photography. He finally finds a picture of her that captures who she really was but it was of her as a little girl.