Søren Kierkegaard was a Danish philosopher, theologian, and writer, born in 1813. He is often considered the father of existentialism, emphasizing individual experience and choice. Kierkegaard's work focused on the complexities of faith, anxiety, and the nature of existence, challenging traditional philosophical and religious views. His most notable concepts include the "leap of faith," which suggests that belief in God requires a personal commitment beyond rational evidence. Kierkegaard's writings, such as "Fear and Trembling" and "Either/Or," explore the struggles of human existence and the importance of personal responsibility in shaping one's life.