Because existentialism is a trend or mood involving philosophical themes rather than a coherent system of philosophy, it is possible to trace through the past a number of precursors to the self-aware existentialism that developed in Europe during the early twentieth century. These precursors involved philosophers who may not have been existentialists themselves, but did explore existentialist themes and thereby paved the way for the creation of existentialism in the 20th century.
Existentialism has certainly existed in religion as theologians and religious leaders have questioned the value of human existence, questioned whether we can ever understand whether life has any meaning, and meditated on why life is so short. The Old Testament book of Ecclesiastes, for example, has a lot of humanist and existentialist sentiments in it - so many that there were serious debates about whether it should even be added to the biblical canon. Among the existentialist passages we find:
As he came forth of his mother's womb, naked shall he return to go as he came, and shall take nothing of his labour, which he may carry away in his hand. And this also is a sore evil, that in all points as he came, so shall he go: and what profit hath he that hath laboured for the wind? (Ecclesiastes 5:15, 16).
In the above verses the author is exploring the very existentialist theme about how a person can find meaning in life when that life is so short and destined to end. Other religious figures have dealt with similar issues: fourth-century theologian Saint Augustine, for example, wrote about how humanity has become alienated from God due to our sinful nature. Alienation from meaning, value, and purpose is something that will be familiar to anyone who reads much existentialist literature.
The most obvious pre-existentialism existentialists, though, would have to be Søren Kierkegaard and Friedrich Nietzsche, two philosophers whose ideas and writings are explored in some depth elsewhere. Another important writer who anticipated a number of existentialist themes was the 17th-century French philosopher Blaise Pascal.
Pascal questioned the strict rationalism of contemporaries like René Descartes. Pascal argued for a fideistic Catholicism that did not presume to create a systematic explanation of God and humanity. This creation of a "God of the philosophers" was, he believed, actually a form of pride. Rather than search for a "logical" defense of faith, Pascal concluded (just as Kierkegaard later did) that religion needed to be based upon a "leap of faith" which was not rooted in any logical or rational arguments.
Because of the issues that are addressed in existentialism, it isn't surprising to find precursors to existentialism in literature as well as philosophy. John Milton's works, for example, evince a great concern for individual choice, individual responsibility, and the need for people to accept their fate - one which always ends in death. He also considered individuals to be far more important than any system, political or religious. He did not, for example, accept the Divine Right of Kings or the infallibility of the Church of England.
In Milton's most famous work, Paradise Lost, Satan is treated as a relatively sympathetic figure because he used his free will to choose what he would do, stating that it is "better to reign in Hell than serve in Heaven." He accepts full responsibility for this, despite the negative consequences. Adam, similarly, does not flee responsibility for his choices - he embraces both his guilt and the consequences of his actions.
Existentialist themes and ideas can be located an a wide variety of works throughout the ages, if you know what to look for. Modern philosophers and writers who identify themselves as existentialists have drawn heavily on this heritage, bringing it out into the open and drawing people's attention to it so that it doesn't languish unnoticed.
