Søren Kierkegaard was a Danish thinker who wrote under several pseudonyms and criticized his country's official Church. For him, faith is not a set of doctrines but a personal and anguished choice before God. He is considered the father of existentialism for placing the concrete individual at the center of philosophy.
Core ideas
The truth that matters is subjective, the one by which one lives and dies
Anxiety arises from awareness of freedom and of possibilities
Faith is a personal leap that goes beyond reason and demands risk
The tradition: Christian existentialist
Christian existentialism focuses on individual existence, choice and anxiety, understood within a personal relationship with God. Kierkegaard is its founder and main reference.