Philosophy
Beauvoir develops an existential ethics for finite people whose freedom depends upon the freedom of others.
The claim that without God everything is permitted gets it backwards. With no outside judge to pardon or justify us, each act becomes a final commitment that we alone must answer for. Values come from human choices, so nothing stands behind us to share the blame.
Being free is not the power to do whatever you like; it is the ability to move beyond your present situation toward an open future. Freedom exists only in concrete, particular projects, and someone who tried to act on the whole universe at once would see all action lose its meaning.
Because freedom is the source of all values, the moral task is to take up its burdens rather than flee them. Choosing to be free and choosing to be moral are the same decision, made again and again. Fleeing freedom is the basic moral failure.
When someone's absolute values collapse, they may swing to rejecting value altogether and deciding to be nothing. They are right that the world comes with no built-in justification, but wrong to stop there: it is up to each person to make the world and their own life worth something.
A person who drifts through incoherent plans, whims, or indifference empties their own actions of meaning. Reasons to live are created only by living actively, so the less someone commits, the less reason they have to exist at all.
Any action that claims to serve humanity must take care not to sacrifice actual people along the way. Freedom takes real, flesh-and-blood form in pleasure and happiness, and if we do not love life for ourselves and through others, no grand justification can make it worthwhile.
Each person is at once a body bound by facts and a consciousness that can step back and choose, and can never settle fully into either. Philosophies have tried to dissolve this split by reducing mind to matter or matter to mind, but the tension cannot be resolved, only lived. Ethics is possible precisely because we are unfinished and can fail.
The 'serious' person escapes the anxiety of choice by treating some cause or value as absolute and simply obeying it, like a child accepting adults' rules as facts of nature. Since the end is placed beyond question, this attitude can excuse cruel acts done in its name.
We act in a world already filled with meanings other people have made, and we can only see and shape it from ground they have laid. Every project is defined by how it meets others' projects, so asserting my own freedom commits me to wanting freedom for others too.
Someone who loves conquest and action for their own sake, without caring about the people affected, shares the nihilist's contempt for others. Given favorable circumstances, such a person easily becomes a dictator. Oppression grows from treating others as mere things rather than free, thinking beings.