Existentialists believe that the fear of death is the primary source of human anxiety because it is the only thing that is certain in life.

Existentialists believe that freedom is the ability to choose your own destiny, even in the face of adversity.

Existentialists believe that choice is a responsibility because it is the only way to create meaning in life.

Existentialists believe that the meaning of life is to create your own meaning through your choices and actions.

Jean-Paul Sartre is best known for his concept of "bad faith", which is the state of being inauthentic or denying one's own freedom.

Albert Camus is best known for his concept of the "absurd", which is the state of being in which the world is meaningless and human existence is futile.

Søren Kierkegaard is best known for his concept of the "leap of faith", which is the act of choosing to believe in something even though there is no rational evidence to support it.

Friedrich Nietzsche is best known for his concept of the "will to power", which is the desire to dominate and control others.

Friedrich Nietzsche is best known for his concept of the "eternal recurrence", which is the idea that everything that has happened will happen again an infinite number of times.

Martin Heidegger is best known for his concept of the "Dasein", which is the German word for "being-there".

Jean-Paul Sartre is best known for his concept of the "authentic self", which is the self that is true to its own nature.

Jean-Paul Sartre is best known for his concept of the "engaged self", which is the self that is actively involved in the world.

Albert Camus is best known for his concept of the "absurd hero", which is the person who confronts the absurdity of life with courage and defiance.

Søren Kierkegaard is best known for his concept of the "knight of faith", which is the person who has the courage to take a leap of faith.

Friedrich Nietzsche is best known for his concept of the "superman", which is the person who has overcome the limitations of human existence.