[1] Søren Kierkegaard suggested that the best use of our capacity for making choices is to freely choose to live a fully human life, rooted in a personal search for values, rather than an external code.
[1] Jean-Paul Sartre said "existentialism is a humanism" because it expresses the power of human beings to make freely-willed choices, independent of the influence of religion or society.
[2] Unlike traditional humanisms, however, Sartre disavowed any reliance on an essential nature of man – on deriving values from the facts of human nature – but rather saw human value as self-created through undertaking projects in the world: experiments in living.
[3] Albert Camus, in his book The Plague, suggests that some of us may choose to be heroic, even knowing that it will bring us neither reward nor salvation;[citation needed] and Simone de Beauvoir, in her book The Ethics of Ambiguity, argues that embracing our own personal freedom requires us to fight for the freedoms of all humanity.
[4] Martin Heidegger attacked Sartre's concept of existential humanism in his Letter on Humanism of 1946, accusing Sartre of elevating Reason above Being.