People in glass houses, says Sennett, turn turtle: ""people can be sociable only when they have some protection from each other,"" they require some ritualized modes of behavior in order to interact effectively. In an original and sweeping historical study, the sociologist author of The Uses of Disorder relates society's most prominent ills, from clinical narcissism to political apathy, to the decline of public life and the rise of an arid privatism, exalting intimacy and enshrining personality. His model is the Enlightenment cosmopolis, where ""a balance of public and private geography. . . did exist""; his method is to investigate the change in public roles--""the social terms on which human beings are expressive""--from the 1750s to the 1890s in the prototypical urban centers, London and Paris. Clothing and speech, he finds, clearly identified who people were in the 18th century, enabling strangers to mingle confidently and (along with other factors) allowing public life to be conducted with civility. In the 19th century, however, industrial capitalism introduced both homogeneity and mystification in dress, as the mass-produced garment ""worn by the Duchesse de X"" was invested with individuality; meanwhile its purchase, in a department store at a fixed price, became a silent, passive act. The growing ""obsession with persons at the expense of more impersonal public relations"" is traced not only in outward forms but in the writings of Rousseau, indicter of the city, and Balzac, who detected and dramatized its social relations ""in the details of personal appearance"" (the same detail that later told all to Sherlock Holmes). In the Dreyfus Affair, finally, a collective personality takes hostile, unalterable form--which Sennett sees echoed recently in the implacable opposition of the Forest Hills Jewish community to a low-income housing project. An enormously rich, complex, and stimulating book with a clear and present purpose: to free us from our private selves.