This thinker criticized proofs of Euclid's parallel postulate since they attempt to use abstract conceptsto show what is clear from perception. He gave 38 ways to win an argument in the sarcastic The Art ofBeing Right. Becoming, Knowing, Being, and Willing are the title concepts of one work by this author. Inaddition to On the Fourfold Root of the Principle of Sufficient Reason, he wrote a work that reexamined the"thing-in-itself." The two title 
This thinker criticized proofs of Euclid's parallel postulate since they attempt to use abstract conceptsto show what is clear from perception. He gave 38 ways to win an argument in the sarcastic The Art ofBeing Right. Becoming, Knowing, Being, and Willing are the title concepts of one work by this author. Inaddition to On the Fourfold Root of the Principle of Sufficient Reason, he wrote a work that reexamined the"thing-in-itself." The two title concepts of that work refer to nature's desire for life and the image of whatis external to the mind. For 10 points, name this pessimistic philosopher who wrote The World as Will andRepresentation.
This thinker criticized proofs of Euclid's parallel postulate since they attempt to use abstract conceptsto show what is clear from perception.
Arthur Schopenhauer