This episode's headline: Summing Up; Gergen & Shields; Final Decision; Return to Somalia. The guests include DAVID GERGEN, U.S. News & World Report; MARK SHIELDS, Syndicated Columnist; CORRESPONDENTS: JEFFREY KAYE; FRED DE SAM LAZARO; CHARLAYNE HUNTER-GAULT. Byline: In New York: ROBERT MacNeil; In Washington: JAMES LEHRER