Simplify the following text for a Grade 9 native English-speaking person.
Original: Arthur Schopenhauer ( 22 February 1788 â `` 21 September 1860 ) was a German philosopher known for his pessimism and philosophical clarity .
Simplified: Arthur Schopenhauer ( February 22 , 1788 â `` September 21 , 1860 ) was a German philosopher .