<DIV>Our current less-is-more impulse may have contemporary trappings, says David E. Shi, but the underlying ideal has been around for centuries. From Puritans and Quakers to Boy Scouts and hippies, our quest for the simple life is an enduring, complex tradition in American culture. Looking across more than three centuries of want and prosperity, war and peace, Shi introduces a rich cast of practitioners and proponents of the simple life, among them Thomas Jefferson, Henry David Thoreau, Jane Addams, Scott and Helen Nearing, and Jimmy Carter.<p>In the diversity of their aspirations and failings, Shi finds that nothing is simple about our mercurial devotion to the ideal of plain living and high thinking. "Difficult choices are the price of simplicity," he writes in the book's revised epilogue. We may hedge a bit in the practice of simple living, and now and then we are driven by motives no deeper than nostalgia. Shi stresses, however, that the diverse efforts to avoid anxious social striving and compulsive materialism have been essential to the nation's spiritual health.</div>