The Theory of Everything: The Origin and Fate of the Universe is an unauthorized 2002 book of some collected works by Stephen Hawking. It was assembled from seven lectures on audiotape by Hawking originally released in 1994 under the title, Stephen W. Hawking's Life Works: The Cambridge Lectures. The book's title is in reference to the theory of everything, a physicists' jargon term for a theory in physics which unifies the four fundamental forces of nature: gravity, the strong force, the weak force, and the electromagnetic force.
Several years ago Stephen Hawking said that there was a fifty-fifty chance that an actual unification of the four fundamental forces – a Theory of Everything – would be achieved. Recently, however, he has become more pessimistic on this score.