Kierkegaard: Father of Existentialism or Critic of Existentialism?

What is Kierkegaard’s relation to existentialism? The lack of clarity of the concept of “existentialism” makes this question difficult. I argue that if we take Sartre as the “ideal type” that defines existentialism, Kierkegaard is better thought of as a critic of existentialism than as its “father.” Kierkegaard rejects both the classical foundationalism that demanded objective certainty as the basis for ethics, and the Sartrean “radical choice” of will that the failure of classical foundationalism led to. Kierkegaard shows how passion and subjectivity can help an individual acquire a truth that can be lived but is not subjective in the sense of being relativistic or arbitrary.