In 1968, John H. Dales, an obscure Canadian economics professor, came back from a sabbatical determined to end what he felt was an endless and meaningless drama between environmental groups and industry over the problem of pollution. After a year of mulling over the problem, he produced a slim book called "Pollution, Property & Prices." It was the classic modest proposal from an academic, and one that the author himself said would never appeal to the opposing sides in this fight. And yet Dales' idea, popularly known as cap and trade, has spread around the globe over the last four decades.