We do not know how to formulate string theory nor do we know its underlying principles. Surprisingly, this fact does not stop us from making progress.
Nathan SeibergThis is a rather unusual situation in physics. We perform approximate calculations which are valid only in some regime and this gives us the exact answer. This is a theorist's heaven- exact results with approximate methods.
Nathan SeibergThe standard model gives us an accuracy of ten decimal digits, this is an amazing success that has never been achieved before in science.
Nathan SeibergI am almost certain that space and time are illusions. These are primitive notions that will be replaced by something more sophisticated.
Nathan Seiberg