Sullivan played Memphis, owner of a Pittsburgh diner about to be torn down, in American Stage’s excellent production of August Wilson’s Two Trains Running. Sullivan’s Memphis was a demanding businessman, an indefatigable justice-seeker, a fast-talking local hero who could also be unreasonable and short-tempered. Again and again, Sullivan showed us Memphis’ strengths and failings as a Rembrandt might: without judgment, without irony, with only a microscopic attention to detail. And the result was, we came away from the character awed by the dazzling, and wondrously inexplicable radiance of his humanity.