What can museums do to emphasize to the public at large that they have a significant role to play in the community, and what can museums do to create a sense of unity of purpose among themselves?"" With more flair than the foregoing suggests, the Director of the Smithsonian - the ""Nation's Attic"" now become the nation's showcase - surveys the past to find answers for the present. Among the Stone Age people of New Guinea he observes collecting as part of the process of discriminating beyond any pragmatic basis; in the mainstream he traces the split in the original Platonic ideal -- the museum as a study center -- which isolated collecting and scholarship, the two to join again in the science museums of the 19th century. Except in the field of classical archaeology, art museums still scant investigation and interpretation; related is the paradoxical schism between Western and advanced Eastern civilizations., studied by art historians, and primitive cultures, including New World archaeology, the province of anthropologists. At present Mr. Ripley, following Levi-Strauss, notes the museum's critical capacity to preserve and record vanishing cultures in the developing nations; also, closer to home -- with the Smithsonian's Anacostia neighborhood museum as a start -- its unique ability to reach the nonreader oriented to objects. For the professional, he has pertinent advice on organizing and labeling exhibits generally; for the all-purpose aesthete, a charming memoir of European museums savored in childhood, Asian museums Visited later. These are discerning, highly civilized reflections for anyone who makes museums his beat, with footnotes that form a fascinating bibliography.