Around the third decade of the 20th century, existentialism emerged in Germany and spread throughout the rest of Europe, especially in France. This school could be interpreted as a reaction to a period of crisis of consciousness on a social and cultural level.
Existentialists claim that man is a being “thrown into the world”, this phrase seems to express the European sentiment of those years and can be interpreted literally: Europeans feel thrown into an inhospitable world, thrown out of their destroyed homes and the safety of their beliefs, values and ideals.
In general, the concept of “existence” is opposed to essence and is not, in principle, a term that can be defined since the definition refers to essence. But for existentialists, this term has a restricted meaning, it is man's own way of being.
Thus only man “exists” properly, since “man” and “existence” are considered synonyms. And in this sense, existence implies freedom and conscience, in the words of Jaspers:
Existence is what is never object; it is the origin from which I think and act, about which I speak in weightings that are not knowledge of something: 'existence' is what refers to and relates to sign itself and, in this, to its own transcendence. Jaspers, Philosophy
Thus, man exists to the extent that he is the origin of himself and makes himself through his free elections. Sartre will say that in man, existence precedes essence... or in other words, that man is freedom:
What we call 'freedom' cannot therefore be distinguished from the being of 'human reality' Sartre, Being and Nothingness
Differently in Heidegger, man's existence does not precede his essence because his essence consists in the very existence.
The consequences of identifying existence with the human being are that things “are” but do not “exist” in a strict sense, and on the other hand, the existence of man can be inauthentic if he renounces his freedom.
For existentialism, to exist is to be in the world and relate to things and other existing beings. But it is not just about being among things, but about moving towards them. This attitude is understood as transcendence, that is, leaving one's consciousness to head toward the World.
Being in the World is something fully active. Man is among the other things, walking among them in an interested (practical) way: he takes care of things, takes care of them. Thus, man creates the only thing that constitutes his' true 'world, a set of relationships between the latter and with respect to man. This is how the human space of the World is constituted.
A central concept within existentialism is that of possibility which identifies with freedom since I am free because I have possibilities and thanks to it is that I make myself.
Not only reason discovers reality, basic feelings like anguish make us experience what existence is better. Kierkegarrd refers to this feeling and distinguishes it from fear because, differing from it, anguish does not have a definite object and arises precisely from the possibilities without guarantees offered by existence.
'Nausea 'of Sartre refers to the absurdity of existence, everything is contingent and there is nothing that can explain existence.