Danish philosopher and theologian, generally acknowledged to be the first existentialist. Born to scholarly and pietistic parents, Kierkegaard enrolled at the university of Copenhagen, then much under the influence of Hegel, in 1830. He rebelled against both the system-building of Hegel, and the formalities of the surrounding Danish Lutheran church. After a period of mild hedonism he completed his religious studies, but, narrowly avoiding marriage, thereafter lived the life of a scholarly recluse. Kierkegaard utterly rejected the Hegelian system as an attempt to put man in the place of God, ignoring the partial, subjective, and limited standpoint from which all human judgement is made. Hence he is led to emphasize the primacy of the will and of free choice unconstrained by reason or cause: where human action and judgement are involved there is no objectivity, no external rails or authority. True to this creed his works are many-sided and apparently contradictory; some were published under pseudonyms, so that he himself could attack them in later work. His influence expanded in the 20th century, in particular amongst thinkers concerned with problems of religious and ethical choice, and especially amongst existentialists concerned with the same problems. His works include Enten-eller (1843, trs. as Either/Or: A Fragment of Life, 1944), Afsluttende Uvidenskabelig Efterskrift (1846, trs. as Concluding Unscientific Postscript, 1941), and Sygdomen Til Døden (1849, trs. as The Sickness unto Death, 1941).
http://www.stolaf.edu/collections/kierkegaard/aboutkierk.html A biography of Kierkegaard
http://www.sorenkierkegaard.org/comment.htm A commentary on Kierkegaard's writings, with a bibliography