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. Much of his philosophical work deals with the issues of how one lives as a "single individual", giving priority to concrete human reality over abstract thinking and highlighting the importance of personal choice and commitment.
Lutheranism is a major branch of Protestantism that emerged under the work of Martin Luther, the 16th-century German friar and reformer whose efforts to reform the theology and practices of the Catholic Church launched the Reformation in 1517. The Lutheran Churches adhere to the Bible and the Ecumenical Creeds, with Lutheran doctrine being explicated in the Book of Concord. Lutherans hold themselves to be in continuity with the apostolic church and affirm the writings of the Church Fathers and the first four ecumenical councils.