Sentence:  A biting , pithy parable of the all pervading hollowness of modern life , the piece has been set by Mlle Lagoon to a sumptuous score ( a single motif played over and over by four thousand French horns ) by <WSD>existentialist</WSD> hot-shot Jean-Paul Sartre . 
Meaning of the word marked with <WSD> tags:  a philosopher who emphasizes freedom of choice and personal responsibility but who regards human existence in a hostile universe as unexplainable