Existentialism is a philosophical school of thought that emphasizes the importance of individual existence, freedom, and choice. It argues that individuals are responsible for creating their own meaning and purpose in life.

Existentialist philosophers argue that the fundamental human condition is anxiety, which arises from the awareness of our own mortality and the meaninglessness of existence.

Authenticity, in existentialism, refers to living in accordance with one's values and beliefs, rather than conforming to societal expectations or seeking external validation.

René Descartes, a French philosopher, is credited with the famous statement 'Cogito ergo sum' ('I think, therefore I am'), which emphasizes the centrality of self-awareness in establishing one's existence.

Existentialist philosophers argue that freedom is not simply the absence of external constraints, but rather the power to choose one's own destiny and create meaning in one's life.

Existentialist philosophers argue that the primary source of human anxiety is the fear of death, which confronts us with the meaninglessness of existence and the inevitability of our own mortality.

Dasein, in existentialism, refers to the unique mode of being of human beings, characterized by their existence in the world, their self-awareness, and their capacity for choice.

Albert Camus, a French-Algerian philosopher and writer, is known for his novel 'The Stranger,' which explores themes of existentialism and absurdity.

Bad faith, in existentialism, refers to the state of being inauthentic, denying one's own freedom, and pretending to be someone one is not in order to conform to societal expectations or gain external validation.

Jean-Paul Sartre, a French philosopher and playwright, is known for his book 'Being and Nothingness,' which explores themes of existentialism and the human condition.

The absurd, in existentialism, refers to the conflict between human reason and the irrationality of the world, which leads to a sense of meaninglessness and futility.

Friedrich Nietzsche, a German philosopher, is known for his book 'Thus Spoke Zarathustra,' which explores themes of existentialism, nihilism, and the Übermensch (superman).

The leap of faith, in existentialism, refers to the act of taking a risk and making a commitment, despite the uncertainty and meaninglessness of existence.

Søren Kierkegaard, a Danish philosopher, is known for his book 'Fear and Trembling,' which explores themes of existentialism, faith, and the individual's relationship with God.

Being-towards-death, in existentialism, refers to the awareness of one's own mortality, which confronts us with the meaninglessness of existence and the inevitability of our own death.