Philosophy
Sartre defends existentialism through freedom, choice and responsibility in a world without predetermined human essence.
A made object is designed first and built afterward, so its purpose comes before it exists. A person is the reverse: they appear in the world first, with no fixed nature, and become only what they make of themselves. On this argument there is no built-in human nature that settles who anyone must be.
A person's character is not a hidden potential waiting behind what they do. It is the total of what they actually do. The coward makes himself cowardly by acting like one, and the hero makes himself heroic the same way, so neither can point to an unused inner talent as proof of who they really are.
If there is no fixed nature or outside plan to blame, then appeals to temperament, upbringing, or circumstance do not take away responsibility. The first step is to make each person see that the full weight of their existence rests on them, and that they are left alone without excuse.
In choosing how to act, a person also proposes what a human being ought to be, acting as a lawmaker for all of humanity. One should always ask what would happen if everyone did the same, and the only way to dodge that question is to deceive oneself.
Anguish is not ordinary anxiety but the feeling of being responsible for others through one's choices. It resembles a commander who must decide with soldiers' lives at stake: the burden does not stop the decision, it accompanies it.
Self-awareness does not happen in isolation, since saying "I think" already puts one in front of other people. We are as certain of others as of ourselves, so individual choices cannot avoid touching a shared human world.
A standing objection is that if everyone creates their own values, no one can condemn anyone else's choices. Critics add that "freedom for its own sake" cannot settle a real moral dilemma without other principles to support it, which leaves open whether this ethic can actually tell people what to do.
Since nothing settles in advance what a person is, they are free whether they want to be or not. Even declining to choose is a choice, so freedom is closer to a sentence than a gift: people are condemned to it.
If no outside authority guarantees moral rules, one cannot simply keep the inherited rules and pretend nothing has changed. Holding on to a secular copy of the old morality while dropping its foundation is a form of dodging the real problem, which is that values must now be chosen and owned.
Since outcomes depend on things beyond one's control, one should commit to action without counting on hope to carry it. The task is to master oneself rather than to wait for the world to cooperate.