What is Sartre's definition of existentialism?

Related questions

1. What is an existentialist hero?
2. What does existential really mean?
3. What is essentialism philosophy?
4. What is the difference between nihilism and existentialism?
5. What is the opposite of existentialism?
6. Why is nihilism true?
7. Will to meaning Kierkegaard?
8. Are existentialists religious?
9. What was Soren Kierkegaard famous for?
10. What are six common themes found in existentialism?

Tags

1. #characterised
2. #evolves
3. #human
4. #existence
5. #existentialism
6. #logically
7. #humanism
8. #later
9. #development
10. #problematic
11. #precedes
12. #theory
13. #sartre
14. #essence
15. #towards
16. #existentialist