Existentialism is a 20th century philosophy that concerned with the analysis of existence and of the way humans finds themselves existing in the world. The main concept of this philosophy is that humans exist first and then each individual spends a lifetime changing their essence or nature. The early 19th century philosopher Soren Kierkegaard regarded as the father of existentialism but the term explicitly adopted by Jean-Paul-Sartre. Nietzsche, Camus, Dostoevsky, Kafka, Simone de Beauvoir and many other philosophers also contributed their works and writings about existentialism. An existentialist could be either a religious moralist, agnostic relativist, or an amoral atheist. Kierkegaard was a religious philosopher, Nietzsche was an anti-Christian, Sartre and Camus was an atheist but each basically agrees that human life is in no way complete and fully satisfying because of suffering and losses that occur when considering the lack of perfection, power, and control one has over their life. Even though they do agree that life is not optimally satisfying, it nonetheless has meaning. Existentialism is the search and journey for true self and true personal meaning in life.