Søren Kierkegaard (1813-1855) was a Danish philosopher, now best known for his book Fear and Trembling. He inspired Existentialist philosophers such as Sartre and Camus. Kierkegaard argued that the lack of certainty in the world led to a feeling of Angst: unfocused fear or anxiety.
The Inheritance of Night was the first title of the early drafts of what later became Styron's first novel, Lie Down In Darkness. The early drafts were thought lost, but have recently been published.
Matthew Arnold's Requiescat can be read here.