Kierkegaard 's philosophy is a philosophy of faith, since he considers that it is the one that saves man from despair, being this a risky 'leap' towards God, in whom 'everything is possible'. Man alone, before God, being nothing but a relationship that relates to himself, contrasts with the concept of Marx and Feuerbach in which man is conceived as a set of social relations.
Kierkegaard's whole thought is a reaction against the idealism and formalist religiosity of the official Danish Church and its theology strongly dominated by Hegelianism. Kierkegaard does so in the name of the value of the individual and of a personal and tragic faith.
Kierkegaard is considered one of the antecedents of 20th century existentialism. Indeed, the fundamental categories of Kierkegaard's thought are those of the existing 'individual' and his' possibilities'. The only real thing is the 'individual', the singular opposite of the Absolute. It is also opposed to the 'people' or the anonymous mass...
Kierkegaard, did not sympathize with the revolutionary and democratic ideals of the 19th century. The loneliness of the individual is tragic, because the singular is confronted with his existence which is not determined by necessity (as in Hegel) but by the 'possibility'. But 'the possible' is infinite and even contradictory, because in the possibility everything is equally possible. Then the alternatives of life cannot be reconciled into a dialectical synthesis and have no solution. The singular feels that he rests on nothing and that he has to choose. Choosing in the world causes you anguish and choosing yourself, despair , which is the 'deadly disease':
Nothing begets anguish (...) The concepts of fear and other similar always refer to something concrete, while 'anguish' is the raw reality, precisely because éte, in its naturalness, is not determined as spirit - Kierkegaard, The concept of anguish
Despair is a disease of the spirit, of the self, and therefore can take three forms: that of the desperate who ignores owning a self (desperation improperly such), that of the desperate who does not want to be himself and that of the desperate who wants to be himself. (...) The relationship between the soul and the body is a simple relationship. On the contrary, if it relates to my sma, then this relationship is the third positive, and this is fully the self - Kierkegaard, The deadly disease