Define existentialism and explain the basic existential concepts of being-in-the-world and nonbeing. Do you ascribe to an existentialist view of the world? Elaborate on your answer and support with some specific examples to illustrate.

Define existentialism and explain the basic existential concepts of being-in-the-world and nonbeing. Do you ascribe to an existentialist view of the world? Elaborate on your answer and support with some specific examples to illustrate.

This is for a Personality Theories course.
Could you cite and reference the following book:
Theories of Personality
Jess Feist, Gregory J. Feist, and Tomi-Ann Roberts, 2018
Mc Graw-Hill Education
ISBN.13: 978-0-077-86192-6