(FORTUNE Magazine) – Harvard's Robert B. Reich is a much admired economist, often stated to be (a) a deep and original thinker and (b) an idea man for various Democratic politicians. His latest work, Tales of a New America (Times Books, $19.95), comes with blurbs from Mario Cuomo and Gary Hart, which might seem to support (b). However, Tales leaves (a) in a certain amount of trouble. Reich is often interesting talking about the ''reigning cultural mythology'' -- the ideas and images that America cherishes. He says the U.S. is always overprepared to believe in ''rot at the top,'' and it alternates in finding the rot in business and government. A central idea of the book is that political debate in the U.S. has grown increasingly sterile. Liberals and conservatives may disagree about who should benefit from different proposals; both, however, assume that economic outcomes require winners and losers. What's needed instead, Reich argues, is a framework for debate in which the country can see its largest opportunities, which characteristically lie in cooperative arrangements -- ways in which both sides gain. But in imposing this framework on a broad range of political, economic, and foreign-policy issues, Reich serves up a lot more preaching than analysis. One example: He says that the U.S. should be less confrontational in dealing with the Japanese on trade policy and must instead seek out ways in which both economies could be ''adding value to a broadly expanding world productive system.'' Exactly how you do this he doesn't say.