Horace Walpole turns to the letters and argues that: Walpole's numerous letters are often used as a historical resource. In one, dating from 28 January 1754, he coined the word serendipity which he said was derived from a "silly fairy tale" he had read, "The Three Princes of Serendip". The oft-quoted epigram, "This world is a comedy to those that think, a tragedy to those that feel", is from a letter of Walpole's to Anne, Countess of Ossory, on 16 August 1776. The original, fuller version appeared in a letter to Sir Horace Mann on 31 December 1769: "I have often said,
Horace Walpole and oftener think, that this world is a comedy to those that think, a tragedy to those that feel – a solution of why Democritus laughed and Heraclitus wept." In "Historic Doubts on the Life and Reign of King Richard III" (1768), Walpole defended Richard III against the common belief that he murdered the Princes in the Tower. In this he has been followed by other writers, such as Josephine Tey and Valerie Anand. This work, according to Emile Legouis, shows that Walpole was "capable of critical initiative". However, Walpole later changed his views following The Terror and declared that