Playwright Wallace Shawn loves to ask difficult questions. Like why do couples who seem so bad for each other stay together (Marie and Bruce)? Or why are arguments tainted with evil the most compelling (Aunt Dan and Lemon)? In his most recent work, The Fever, which recounts the identity crisis he suffered when he became deathly ill traveling in an unidentified Latin American country, Shawn asks the most bedeviling question of all: How can a man of liberal convictions continue to live in comfort knowing that his love of luxury depends upon the exploitation of people poorer and less fortunate than himself? In bringing Shawn's harrowing monologue to life, actor David Shapiro pulls no punches and uses no cheap tricks to keep our attention. Performing on a mostly bare stage, using only his voice and a few spare gestures, Shapiro makes us feel the full intensity of Shawn's hour-long inward Journey. As Shawn descends into his fever-inspired private hell of self-doubt and self-examination, Shapiro pulls us down with him, showing every step Shawn's discovery of a world far less cozy than the fashionable Manhattan of his youth. The Fever is as much a philosophical tract as it is a work of dramatic literature, both understandable and intriguing, compelling and infuriating. Anyone who leaves this performance without feeling stirred up has not been paying attention. Chicago Dramatists Workshop, 1105 W. Chicago, 633-0610. Through November 25: Mondays-Wednesdays, 7:30 PM. $7.