For 10 points, name this English philosopher who collaborated with Alfred North Whitehead on Principia Mathematica.
One paper by this author rejects Meinong's theory that all grammatically correct phrases stand for real objects. This philosopher examined the truth value of statements about non-existent objects with the sentence "The present King of France is bald." This philosopher introduced the "theory of types" to solve the problem of whether the set of all sets that are not members of themselves contains itself, a paradox named for this author of On Denoting. With an older philosopher, he wrote a work that attempted to derive mathematics using symbolic logic. For 10 points, name this English philosopher who collaborated with Alfred North Whitehead on Principia Mathematica.
One paper by this author rejects Meinong's theory that all grammatically correct phrases stand for real objects.
Bertrand Russell