There is a line that separates a good actor from a ham, a line that rings itself invisibly around the stage, separating audiences from performers and the performances. It is one that Naseeruddin Shah knows never to cross. The man who owns the stage the moment he steps on it — be it to read T S Eliot or tease out the nuances in an Ismat Chughtai story or, as he has been doing for a month and more, to walk the stage as an Alzheimer’s-ridden old man — says that most actors make the cardinal mistake of wanting to