To unify, or reconcile, these two theories, string theory was introduced as a proposed “theory of everything”. Since both quantum physics and general relativity have been proven true for the most part, we seem to just be missing the central piece of the proverbial physics puzzle. String theory is a bold attempt to fill in the blanks on what we don’t know about the universe, and though it may seem bizarre, famous wheelchair-bound physicist Dr. Stephen Hawking is on the record for stating that string theory is “the only candidate for a complete theory of the universe.”.