Like other philosophical concepts, existentialism often escapes a simple definition. Generally speaking, though, existentialism can be described as a philosophy that emphasizes the uniqueness and isolation of the individual as he or she experiences a hostile and indifferent universe. Common themes within existentialism are individual existence, freedom, uncertainty, subjectivity, responsibility, and choice. As such, existentialism addresses the nature and purpose of human existence.
Unlike other philosophical systems that focus on metaphysical issues, existentialism focuses more on how people should practically live. Essential to existentialism is its pessimism regarding the ability to find true knowledge or know anything with certainty. This uncertain nature of life can lead to dread and a sense that life is absurd and meaningless. The solution to doubt and dread, though, is to choose to believe passionately in something whether it be God or a certain political philosophy or something else. This passionate commitment to something is what gives meaning to life. You may not know for sure that your belief system or what you choose to believe in is correct but you need to follow it passionately anyway.
Also linked to existentialism is the view that truth is subjective. Thus, truth is related to the individual and not to some universal objective standard. As the founder of existentialism, Soren Kierkegaard stated, “The thing is to find a truth which true for me, to find the idea for which I can live and die.”
Existentialists strongly advocate that individuals have the freedom to choose their own way. Humans are not simply beings who act according to a predetermined nature. It is the choices people make that determine their nature. As existentialist philosopher Jean-Paul Sarte stated, “Existence precedes essence.” By this he means that we are all thrown into existence first without a predetermined nature. Only later do we construct our nature or essence through our actions.
Existentialism can be applied broadly. Kierkegaard applied it to Christianity and ethics while Sarte tried to combine existentialism with Marxism and atheism. In addition to Kierkegaard and Sarte, other notable existentialist philosophers include Martin Heidegger, Karl Jaspers, and Simone de Beauvoir.