The nineteenth century Danish thinker, Soren Kierkegaard, is usually said to be the father of existential philosophy. Kierkegaard, however, was largely ignored in his time and the philosophy of existence did not begin to take firm root in Europe until after the First World War. At that time there was a renewed interest in Kierkegaard in Germany. Both Karl Jaspers and Martin Heidegger credit Kierkegaard with the existential understanding of the concept of existence. The existentialist approach to philosophy spread rapidly in Europe during World War II, and it gained new prominence following the War through the writings of the French philosopher and man of letters, Jean-Paul Sartre. It was slower to find a home in the English speaking world, but soon after the War it began to gain strength, particularly among English speaking theologians and philosophers of religion who were searching for alternatives to idealism and logical positivism. Existential philosophers are united not so much by a set of doctrines as by an approach to philosophy. It is a way of thinking that begins with human existence. Existence refers not to an abstract essence, but to the concrete temporal way of being that distinguishes human beings from other beings. Human beings exist not merely in the sense that they are entities that we come across in the world. Human beings have a relationship to their existence, and their existence is understood in terms of possibility, possible ways of being. They are beings who give direction to their being, who are unfinished, always on the way. They are acting beings, agents, rather than merely rational or intellectual beings. For some existential thinkers, this going beyond or transcending leads to nothingess. We are understood to be thrown back upon ourselves, to create our being out of nothing, so to speak. For others, this going beyond leads to being, transcendence, or even to God, where human fulfillment may be understood to be dependent upon the graciousness of being or God.