Q. Can a Jew be an existentialist?
A. In order to answer your question I looked up the word in one of the dictionaries in my study. It told me, “Existentialism: a modern philosophical movement stressing the importance of personal experience and responsibility and the demands that they make on the individual, who is seen as a free agent in a deterministic and seemingly meaningless universe”. There are Jewish existentialists like Buber, Rosenzweig and Herberg, but there is no one existentialism and some versions may not accord with Jewish teaching.
One brand of existentialism has a strongly christological approach; think of the names Kierkegaard chooses for his books, names like “Fear and Trembling”, “The Absurd”, “The Crisis”, based on mistrust of human reason and nature. The idea that out of despair man comes to God has its reflections in some Jewish sources, but whilst Judaism is fascinated by the nature of human experience it does not as a whole go along with a doctrine that man is lost in a cold, unfeeling world.
Contrast Kierkegaard’s books with those of Abraham Joshua Heschel: “God in Search of Man”, “Man’s Quest for God”, “Man is not Alone”, etc. As a Jewish philosopher Heschel looks at God and man yearning for one another but finds pathways to God in more “normal” aspects of the human condition such as the feeling of amazed, wondering awe and the mind’s capacity to be stretched.