Soren Kierkegaard, who was born in Denmark and died there at the age of forty-two, is regarded by many as the father of existentialist thinking. During his lifetime the Hegelian theologian he reacted against the Hegelian theologists in Denmark, denounced organized religion and held that the act of choice by an individual was all-important.

The Diary covers the important elements in Kierkegaard's life, including his childhood, his relations with his father, the influence of other writers on him, his broken engagement (which had a far-reaching effect on the rest of his life), and his celebrated quarrel with the Church.

Kierkegaard's writings are important because he is almost the first European writer to take a modern, analytical, psychological approach to religion. Proust, Joyce, and Aldous Huxley were only a few of the modern writers influenced by the Dane; and Jean-Paul Sartre's philosophy of existentialism is based on his thinking.