THE SUBSTANCE OF FIRE, by Jon Robin Baitz, is a play by a young writer that has all the hallmarks of what used to be called a "good evening of theater—” witty, intelligent, literate writing, deep passions and a tour-de-force leading role. Even though the outward form of the play is that of a family drama—in this case, a family struggling to control its New York publishing house—the play is really a character study in two distinctly different acts. In the first, Isaac Geldhart, proud publisher and family patriarch, copes with his three children as they scheme to remove him from his job. In the second and more contemplative act, we see a bitter man coping with the loneliness and the unfortunate results of his inability to love. If this were an ancient Greek play, the first part would have been called "The King" and the second "The King in Exile."