Either/Or,

Søren Aabye Kierkegaard was a Danish theologian, philosopher, poet, social critic, and religious author who is widely considered to be the first existentialist philosopher. He wrote critical texts on organized religion, Christianity, morality, ethics, psychology, and the philosophy of religion, displaying a fondness for metaphor, irony, and parables.

Kierkegaard's theological work focuses on Christian ethics, the institution of the Church, the differences between purely objective proofs of Christianity, the infinite qualitative distinction between man and God, and the individual's subjective relationship to the God-Man Jesus Christ, which came through faith.