Soren Kierkegaard founds existentialism in 1843.

In addition to the philosophy of dialogue, existential philosophy has its point of origin in Kierkegaard and his concept of individuality

Kierkegaard's philosophical book Fear and Trembling is first published on October 16, 1843.

Kierkegaard publishes some of his works using pseudonyms and for others he signs his own name as author.

Whether being published under pseudonym or not, Kierkegaard's central writings on religion have included Fear and Trembling and Either/Or, the latter of which is considered to be his magnum opus.

Pseudonyms are used often in the early nineteenth century as a means of representing viewpoints other than the author's own; examples include the writers of the Federalist Papers and the Anti-Federalist Papers.

Kierkegaard employs the same technique as a way to provide examples of indirect communication.

In writing under various pseudonyms to express sometimes contradictory positions, Kierkegaard is sometimes criticized for playing with various viewpoints without ever committing to one in particular.

He has been described by those opposing his writings as indeterminate in his standpoint as a writer, though he himself has testified to all his work deriving from a service to Christianity.

After On the Concept of Irony with Continual Reference to Socrates, his 1841 doctoral thesis under Frederik Christian Sibbern, he had written his first book under the pseudonym "Johannes Climacus" (after John Climacus) between 1841–1842.

De omnibus dubitandum est (Latin: "Everything must be doubted") will not be published until after his death.

Kierkegaard's magnum opus Either/Or had been published February 20, 1843; it was mostly written during Kierkegaard's stay in Berlin, where he took notes on Schelling's Philosophy of Revelation.

Either/Or includes essays of literary and music criticism and a set of romantic-like-aphorisms, as part of his larger theme of examining the reflective and philosophical structure of faith.

Edited by "Victor Eremita", the book contains the papers of an unknown "A" and "B", which the pseudonymous author claims to have discovered in a secret drawer of his secretary.

Eremita has a hard time putting the papers of "A" in order because they are not straightforward.

"B"'s papers are arranged in an orderly fashion.

Both of these characters are trying to become religious individuals.

Each approaches the idea of first love from an esthetic and an ethical point of view.

The book is basically an argument about faith and marriage with a short discourse at the end telling them they should stop arguing.

Eremita thinks "B", a judge, makes the most sense.

Kierkegaard stresses the "how" of Christianity as well as the "how" of book reading in his works rather than the "what".

Three months after the publication of Either/Or, May 16, 1843, he publishes Two Upbuilding Discourses, 1843 and continues to publish discourses along with his pseudonymous books.

These discourses are published under Kierkegaard's own name and are available as Eighteen Upbuilding Discourses today.

On October 16, 1843, Kierkegaard publishes three more books about love and faith and several more discourses.

Fear and Trembling is published under the pseudonym Johannes de Silentio.

Repetition is about a Young Man (Søren Kierkegaard) who has anxiety and depression because he feels he has to sacrifice his love for a girl (Regine Olsen) to God.

He tries to see if the new science of psychology can help him understand himself.

Constantin Constantius, who is the pseudonymous author of that book, is the psychologist.

At the same time, he publishes Three Upbuilding Discourses, 1843 under his own name, which deal specifically with how love can be used to hide things from yourself or others.

These three books, all published on the same day, are an example of Kierkegaard's method of indirect communication.

Kierkegaard questions whether an individual can know if something is a good gift from God or not and concludes by saying, "it does not depend, then, merely upon what one sees, but what one sees depends upon how one sees; all observation is not just a receiving, a discovering, but also a bringing forth, and insofar as it is that, how the observer himself is constituted is indeed decisive."

God's love is imparted indirectly just as our own sometimes is.