"Americans are driven by many forces, and chief among those forces--and thus a formative element in the country's soul--is the "pursuit of happiness" of which Jefferson wrote in the Declaration of Independence. When he composed those words in his rented second-floor quarters at Seventh and Market in Philadelphia in late June, 1776, Jefferson was not thinking about happiness in only the sense of good cheer. He and his colleagues were contemplating something more comprehensive--more revolutionary. Garry Wills's classic 1978 book on the Declaration, Inventing America, put it well: "When Jefferson spoke of pursuing happiness," Wills wrote, "he had nothing vague or private in mind. He meant public happiness which is measurable; which is, indeed, the test and justification of any government."