Sherlock Season 4: 20 Easter Eggs & References In 'The Final Problem'
18. Oscar Wilde
Mycroft quotes Oscar Wilde's The Importance of Being Earnest when he says that "truth is rarely pure and never simple."
A reference to Wilde is an apt one for Sherlock to make, seeing as the Victorian writer should be thanked for indirectly inspiring Arthur Conan Doyle to continue writing Sherlock Holmes stories.
Wilde and Doyle attended a dinner party together one night in 1889 and had a discussion about the depictions of evil in fiction that got the creative juices flowing. This led Wilde to write The Picture of Dorian Gray and Doyle to resurrect Holmes for his second novel The Sign of the Four.