Existentialism

Existentialism was a school of philosophy. One could suffer an existential crisis in life, (PROSE: The Avant Guardian, Lonely) as well as experience existential angst (PROSE: Jealous, Possessive) and despair. (PROSE: Snowman in Manhattan)

Abney was reading a book on existentialism—Jean-Paul Sartre's Huis Clos—in his school library when he was killed. (PROSE: Long Term)

The idea that a robot personality matrix really believed itself to be the Seventh Doctor made Forgwyn "go existential all over". Bernice Summerfield asked, "What's the difference between a real personality and a created one, if the created one is endowed with a belief in its autonomous existence?" (PROSE: Tragedy Day)

The Eighth Doctor recognised that Jamon de la Rocas was going through a "somewhat rocky existential time of late", "worrying about the existence of self, souls, prana and whatnot". He promised Jamon that, while in other sections of the galaxy such things were still a mystery, in the Slow Empire, they could be certain that such things existed, as there was no other explanation as to how they used his to control him. (PROSE: The Slow Empire)

Imogen Quaye learned about existentialism quickly due to the experiments done to her, as well as about Homeric poetry, stereography, evolutionary theory and palaeontology. (PROSE: Artificial Intelligence)