Søren Kierkegaard was a Danish philosopher, theologian, poet, social critic and religious author who is widely considered to be the first existentialist philosopher. He wrote critical texts on organized religion, Christendom, 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. The Soren Kierkegaard Collection features: Fear and Trembling Philosophical Fragments Purity of Heart Is to Will One Thing and The Sickness Unto Death