Happy Birthday, Soren Kierkegaard!

As noted in Writer's Almanac (American Public Media, Garrison Keillor):
May 5 is the birthday of Danish philosopher Søren Kierkegaard, born in Copenhagen (1813). He was the youngest of seven children, a sickly boy, and his father used to take him for imaginary walks indoors during bad weather, describing all kinds of wonderful and imaginary sights. Kierkegaard’s father was a wealthy wool merchant who had retired young, and when he died he left his son enough money to be financially independent for the rest of his life. Kierkegaard was a homebody, and rarely left Copenhagen. He enjoyed going to the theater, taking carriage rides out into the country, and chatting with people — even servants and laborers — that he met while strolling the streets. He wrote, “I had real Christian satisfaction in the thought that, if there were no other, there was definitely one man in Copenhagen whom every poor person could freely accost and converse with on the street.”
Kierkegaard is widely considered the father of existential philosophy. His work touched not only philosophy, but also theology, psychology, literary criticism, and fiction. He also came up with two concepts that are commonplace to us today: one is “subjectivity,” the idea that we all perceive the world — and “truth” — differently; and the other is the fact that faith is not possible without doubt. One must doubt the existence of God to have faith in the existence of God. Belief without doubt is just credulity. He published several books at his own expense, including Either/Or (1843), Works of Love (1847), and The Sickness Unto Death (1849). He published many works under a variety of aliases: Victor Eremita, Johannes de Silentio, Anti-Climacus, Hilarius Bookbinder, and Vigilius Haufniensis. He did so, he said, to disavow his own authority. He would adopt a “character” who wrote about a particular philosophical viewpoint, and then would adopt another persona to explore the opposing viewpoint.
Kierkegaard wrote: “It is quite true what philosophy says; that life must be understood backwards. But then one forgets the other principle: that it must be lived forwards.”