TALLAHASSEE, Florida (AP) — Darrin McMahon still cannot define happiness after spending six years researching and writing a book about it.While that’s been a frustration, the Florida State University history professor said it’s also what gives happiness its power and allure.

His book, “Happiness: A History”, was recently named by The New York Times as one of the 100 notable books of 2006.

It traces what the great thinkers of Western philosophy have thought about happiness. They include Aristotle, Socrates, Locke, Rousseau, Darwin, Marx, Freud and Thomas Jefferson, who famously counted “the pursuit of Happiness” as an “unalienable right” in the Declaration of Independence.

“The book is more about the pursuit than the attainment, because in some ways you never get there,” McMahon said in an interview.

“Happiness, as I try to argue in the book, tends to slip away from you when you think about it too much.”

He got the idea for the book while teaching at Columbia University in New York during the 1990s. The Berlin Wall had fallen and the world appeared headed for democracy. The stock market was booming and most people seemed to be prospering.

“Happiness was in the air,” McMahon recalled. “Clinique, the cosmetics company, came out with a perfume called Happy; you could still remember the Bobby McFerrin song ‘Don’t Worry, Be Happy’.”

Happiness also dovetailed nicely with McMahon’s academic focus on the 17th and 18th centuries, the period of Enlightenment, when Jefferson and others put a new spin on the subject.

Until then, most people didn’t think of it as a right, unalienable or otherwise. It was more a matter of luck or virtue.

“The concept of luck is embedded in the very word happiness — luck or fortune,” McMahon said. “That’s true in every Indo-European language. It’s a really striking thing, all the way back to the ancient Greek and moving forward.”

Happiness is linked to such words as happen and happenstance. Greek tragedies were filled with the idea that happiness was a matter of fate.

“The Gods are spiteful and capricious,” McMahon said. “Just when you think everything’s going well, they pull the rug out from you and send a thunderbolt down.”

That began to change with Socrates, but the concept of humans having some control over their own happiness didn’t flower until the 18th century.

“If you ask somebody today what happiness is, they’ll inevitably tell you that it involves feeling good,” McMahon said.

But it meant something more to the Greeks and Romans. Aristotle held that happiness was based on a lifetime of experience. You couldn’t really tell if you were happy until you were dead. Many felt virtue was the key to happiness even though it took suffering to achieve.

Cicero once said a virtuous man could be happy even while being tortured.

Christianity maintained the link between virtue and happiness. During the Enlightenment, though, thinkers began to focus more on pleasure and the ability of people to pursue, if not always attain, happiness.

While pleasure today has become virtually synonymous with happiness, McMahon believes the older concept of a life well lived has not been entirely lost.

“You push most people and they will admit that, well, it’s not enough to be happy simply to be pleasured as it were,” he said. “You need other things, and they’ll talk about family and they’ll talk about love and they’ll talk about meaning and so forth.”