Existentialism is a way of thinking that focuses on what it means for people to exist. It is a philosophical movement. It became well-known in books and movies of the 19th and 20th centuries. Existentialism is known for dealing with nihilistic problems, but is generally still a kind of . It says that humans have will and consciousness, but they live in a world that does not. The premise that people must make choices about their life while knowing they are mortal is what existentialism is all about.

It was started by the Danish philosopher Søren Kierkegaard (18131855).
Kierkegaard was a very religious man, but existentialism in the 20th century became more and more atheistic. Most of its main thinkers and writers were in mainland Europe. For example, Jean-Paul Sartre spent most of the Second World War in a German prison camp, reading the philosophy of Martin Heidegger. When he came out he gave a lecture called Existentialism and Humanism. This early lecture may be easier to read than his later work.

Many religions and philosophies (ways of thinking about the world) say that human life has a meaning (or a purpose). But people who believe in existentialism think that the world and human life have no meaning unless people give them meaning: ‘existence precedes [is before] essence’. This means that we find ourselves existing in the world, and then we give ourselves meaning, or 'essence'. As Sartre said, "We are condemned to be free". This means that we have no choice but to choose, and that we have full responsibility for our choices. Another way to put it is that we are always making choices even if we don't realize it.

Existentialists believe that our human 'essence' or 'nature' (way of being in the world) is simply our 'existence' (being in the world). More simply put, the 'essence' of a human, or what makes a human a 'human', is not due to nature or uncontrollable circumstances; rather, human essence is really just what we choose to make it. This means that the only nature we as humans have is the nature we make for ourselves. As a result of this, existentialists think that the actions or choices that a person makes are very important. They believe that every person has to decide for themselves what is right and wrong, and what is good and bad.

People who believe in existentialism ask questions like ’what is it like to be a human (a person) in the world?’ and ’how can we understand human freedom (what it means for a person to be free)?’ Existentialism is often connected with negative emotions, such as anxiety (worrying), dread (a very strong fear), and mortality (awareness of our own death). Some existentialists, like Sartre and Heidegger, think that thinking about these emotions helps people to choose the way that they want to live their lives.

Existentialism is sometimes confused with nihilism.  It is different from nihilism, but there is a similarity. Nihilists believe that human life does not have a meaning (or a purpose) at all; existentialism says that people must choose their own purpose.

Existentialism in books 
Many of the main sources for existentialism were written in other languages and only later translated, mostly after the 1950s.

The Outsider,  by Colin Wilson (1956), examined the idea of the social outsider in modern society. It was one of the few books in English to give a readable explanation of the ideas and writings of Dostoyevsky, Sartre and Camus, especially the idea of alienation.
Irrational Man: a study in existential philosophy, by William Barratt (1958), Anchor Books . This is a more direct study of existentialism by a professional philosopher. It introduced the idea of existentialism as a philosophy.
 Franz Kafka wrote books about people who feel hopeless because they are trapped in absurd (meaningless or senseless) situations that they do not understand.
 Fyodor Dostoevsky, a Russian writer, wrote novels such as Crime and Punishment and The Brothers Karamazov. Dostoevsky also wrote Notes from Underground, which is the story of a man who cannot fit into society and who feels alienated.
 Hermann Hesse is a writer who wrote the book Steppenwolf in 1928. Hesse used an existentialist idea from Kierkegaard to write this book.
 Jean-Paul Sartre wrote novels such as Iron in the Soul that have existential themes. The people in Jean-Paul Sartre's stories often faced death, and had to make hard choices.
 Albert Camus wrote novels such as The Stranger that had stories about existentialism. The Stranger tells the story about a man who does not have feelings (emotions) after his mother dies. The man does not believe in God. The man does not have feelings (emotions) after he murders (kills) an Arab man.

Existentialism in movies 
Ingmar Bergman made a movie called The Seventh Seal in 1957. It shows the doom and gloom of the late Middle Ages caused by the Black Plague, famine, the Hundred Years' War between France and England, and papal schism. 
 
The movie Taxi Driver (which has the actor Robert De Niro) from 1976 has existential ideas in it. The main character feels sad and lonely, because he cannot understand the world.
Jean-Luc Godard's "Vivre sa vie (film)" and Federico Fellini's 8 1/2 are prime examples of the Existentialism fashion in the European early 50's that influenced American films such as Easy Rider or The Graduate in the 1960s.

I Heart Huckabees is a 2004 film directed by David O. Russell. The movie revolves around a man who hires two existential detectives to find out about his "coincidence." He meets his "other" and is tempted with the dark side of existentialism.

References 

Philosophical movements and positions