Task: Text Categorization
Input (English): This thinker discusses the truth of the phrase "the golden mountain does not exist" in a work that criticizes Alexius Meinong for his belief an object could exist that is both round and not round. He distinguished between "knowledge by description" and "knowledge by acquaintance" in his book The Problems of Philosophy. He argues definite descriptions are "incomplete symbols" while discussing the phrase "The present king of France is bald" in his essay "On Denoting." This author of Why I'm Not a Christian wrote a work, which tries to resolve his namesake paradox that "the set of all sets must contain itself." For 10 points, name this philosopher who wrote Principia Mathematica with Albert North Whitehead.
Output (English): Social Science