The elusive butterfly of happiness has been fluttering before humanity for a long time. America's Thomas Jefferson declared the pursuit of it an inalienable human right over 220 years ago. But a good 1,800 years or so before that, another great farmer-philosopher had seen the urge to chase happiness as an inalienable human instinct, alive and well long before the age of entitlement. "We work hard at doing nothing," observed Horace caustically of his fellow Romans. "We seek happiness in yachts and four-horse conveyances. (Yet) what you seek is here. . . ."

Jefferson, a consummate politician as well as a philosopher, refrained from defining what he meant by happiness. Horace, as a poet, was less constrained, but even he tended to write about it more in terms of what it was not than what it was -- not travel, not ambitious business schemes, not expensive diversions and luxuries, but a quiet, frugal, settled life. A random memory check confirms the wisdom of such circumspection: Attempts to pin down happiness have inspired some wildly varying definitions, all appealing, but none authoritative.

"A Jug of Wine, a Loaf of Bread -- and Thou" were paradise enough for the 11th-century Persian poet Omar Khayyam. Nine centuries later, John Lennon opted for an even more radical simplicity with his view of happiness as "a warm gun" (although he probably had a Thou in mind as well as he sang this). In between came no-nonsense Victorians like Charles Dickens' Mr. Micawber, who wasn't having any of that romantic antimaterialism. "Annual income twenty pounds, annual expenditure nineteen nineteen six, result happiness," he said firmly. "Annual income twenty pounds, annual expenditure twenty pounds ought and six, result misery."