Whenever you work on something and try to solve one problem, and you e — Nathan Seiberg

"Most string theorists are very arrogant ... If there is something [beyond string theory], we will call it string theory."

"The quantum dualities, which are known as S-duality or U-duality, extend the classical T-duality and lead to a beautiful and coherent picture of stringy dualities. These exchange highly quantum situations with semiclassical backgrounds, exchange different branes, etc. As in the classical dualities, among all dual descriptions there is at most one description which is natural because it is semiclassical. All other dual descriptions are very quantum mechanical."

"Ultimately, we hope to find a fundamental theory that explains everything with no input parameters."

"Supersymmetry arises naturally in string theory. (It was originally motivated by string theory.)"

"Gravity is not an option in string theory. It is a logical consequence of it!"