and his or her awareness of sinfulness. Here are several quotes from Kierkegaard's where he discusses his concept of sin. Kierkegaard's thoughts on other philosophers Kierkegaard and Fichte Kierkegaard wrote much about Johann Gottlieb Fichte in his thesis The Concept of Irony as well as in his first book De omnibus dubitandum est, written under the pseudonym Johannes Climacus, and his Journals. Fichte wrote the book The Vocation of Man (1800) which called for a progression in the life of the human being from doubt to knowledge and then to faith. De omnibus dubitandum est is from Descartes and means everything must be doubted. Both Kierkegaard and Fichte were interested in this idea of beginning with doubt as well as subjectivity. Kierkegaard wrote: "In Fichte, subjectivity became free, infinite, negative. But in order for subjectivity to get out of this movement of emptiness in which it moved in infinite abstraction, it had to be negated; in order for thought to become actual, it had to become concrete." Kierkegaard and Hegel Many philosophers think that one of Kierkegaard's greatest contributions to philosophy is his critique of Georg Wilhelm Friedrich Hegel. Indeed, many of Kierkegaard's works are written in response to or as a critique of Hegel. Although Kierkegaard strongly criticized some aspects of Hegelian philosophy, his work also shows that he was also positively influenced by Hegel, and had respect for Hegel himself. In a journal entry made in 1844, Kierkegaard wrote: While Kierkegaard was a student of theology at the University of Copenhagen, Hegelianism had become increasingly popular. Johan Ludvig Heiberg and Hans Lassen Martensen were key figures in Danish Hegelianism. Kierkegaard remarked in his journal on 17 May 1843 that Heiberg's writings were "borrowed" from Hegel, implying Heiberg would have been a nobody without Hegel. Kierkegaard objected to Hegel's claim that he had devised a system of thought that could explain the whole of reality, with a dialectical analysis of history leading the way to this whole. Hegel claimed that the doctrines and history of Christianity could be explained as a part of the rational unfolding and development of our understanding of the natural world and our place within it. Kierkegaard considered Hegel's explanation of Christianity as a necessary part of world history to be a distortion of the Christian message and a misunderstanding of the limits of human reason. He attempted to refute this aspect of Hegel's thought