Who is Liv Ullman from Necessary Losses and what is their importance?

Judith Viorst refers to Liv Ullman as being responsible for teaching her that in acting, only a character who contains both good and bad, is convincing. She refers to a scene in The Chalk Garden , in which she (Ullman) finds a baby and decides to take the baby with her. However, in playing this role optimally, Ullman had to hesitate, to doubt, be afraid and not represent complete goodness. Viorst notes that Ullman has been called "the world's most charismatic actress."