Existentialism entered the American consciousness like an elephant entering a dark   room: there was a good deal of breakage and the people inside naturally mistook  the nature of the intrusion. What would it be? An engine of destruction perhaps, a   tank left over from the war? After awhile the lights were turned on and it was   seen to be "only" an elephant; everyone laughed and said that a circus must be   passing through town. But no, soon they found that the elephant was here to stay;   and then, looking closer, they saw that although he was indeed a newcomer, an odd-looking one at that, he was not a stranger: they had known him all along.  This was in 1946 and 1947. And in no time at all Existentialism became a common compoun.
No question of what it meant; it meant the life re-emerging after the war in the cafés of the Left Bank---disreputable young men in paint-smeared jeans, and  their companions, those black-stockinged, makeupless girls who smoked too many cigarettes and engaged in who knows what follies besides. And their leader,  apparently, was this fellow Sartre, who wrote books with loathsome titles like rNausea and The Flies. What nonsense, the wiseheads concluded. Perfectly safe to  dismiss it as a fad, very likely a hoax.

Meanwhile at centers of serious thought the texts of Existentialists, especially Sartre's, were being translated and studied, with a resulting profound shock to   the American intellectual establishment. On one hand the Neo-Thomists and other  moral philosophers were alarmed by Existentialism's disregard for traditional  schemes of value; on the other the positivists and analytical philosophers were  outraged by Existentialism's willingness to abandon rational categories and rely on  conmental processes of consciousness. Remarkably violent attacks issued from both r these camps, and set off all the more sharply by the enthusiasm, here and there, ofr small welcoming bands of the avant garde. That the welcomers were no less informed about Existentialism than the attackers, didn't help matters.

Nevertheless Existentialism, gradually and then more rapidly, won adherents,  people who took it seriously. Someone has said that Existentialism is a  philosophy---if a philosophy at all---that has been independently invented by millions of people simply responding to the emergency of life in a modern world. Coming to the first time to the works of Sartre, Jaspers, or Camus is often like reading, on page after page, one's own intimate thoughts and feelings, expressed  with new precision and concreteness. Existentialism is a philosophy, as a matter of  fact, because it has been lengthily adumbrated by men trained in the philosophical diciplines; but it is also and more fundamentally a shift in ordinary human attitudes  that has altered every aspect of life in our civilation.

 
                                                                    --Hayden Carruth