Sherlock Holmes (/ˈʃɜːrlɒk ˈhoʊmz/) is a fictional detective created by British author Arthur Conan Doyle. Referring to himself as a "consulting detective" in his stories, Holmes is known for his proficiency with observation, deduction, forensic science and logical reasoning that borders on the fantastic, which he employs when investigating cases for a wide variety of clients, including Scotland Yard.
Conan Doyle repeatedly said that Holmes was inspired by the real-life figure of Joseph Bell, a surgeon at the Royal Infirmary of Edinburgh, whom Conan Doyle met in 1877 and had worked for as a clerk. Like Holmes, Bell was noted for drawing broad conclusions from minute observations.[13] However, he later wrote to Conan Doyle: "You are yourself Sherlock Holmes and well you know it".[14] Sir Henry Littlejohn, Chair of Medical Jurisprudence at the University of Edinburgh Medical School, is also cited as an inspiration for Holmes. Littlejohn, who was also Police Surgeon and Medical Officer of Health in Edinburgh, provided Conan Doyle with a link between medical investigation and the detection of crime.[15]
Holmes observes the dress and attitude of his clients and suspects, noting skin marks (such as tattoos), contamination (such as ink stains or clay on boots), emotional state, and physical condition in order to deduce their origins and recent history. The style and state of wear of a person's clothes and personal items are also commonly relied on; in the stories, Holmes is seen applying his method to items such as walking sticks,[108] pipes,[109] and hats.[110] For example, in "A Scandal in Bohemia", Holmes infers that Watson had got wet lately and had "a most clumsy and careless servant girl". When Watson asks how Holmes knows this, the detective answers: It is simplicity itself ... my eyes tell me that on the inside of your left shoe, just where the firelight strikes it, the leather is scored by six almost parallel cuts. Obviously they have been caused by someone who has very carelessly scraped round the edges of the sole in order to remove crusted mud from it. Hence, you see, my double deduction that you had been out in vile weather, and that you had a particularly malignant boot-slitting specimen of the London slavey.[111] In the first Holmes story, A Study in Scarlet, Dr. Watson compares Holmes to C. Auguste Dupin, Edgar Allan Poe's fictional detective, who employed a similar methodology. Alluding to an episode in "The Murders in the Rue Morgue", where Dupin determines what his friend is thinking despite their having walked together in silence for a quarter of an hour, Holmes remarks: "That trick of his breaking in on his friend's thoughts with an apropos remark ... is really very showy and superficial."[112] Nevertheless, Holmes later performs the same 'trick' on Watson in "The Cardboard Box"[113] and "The Adventure of the Dancing Men".[114] Though the stories always refer to Holmes's intellectual detection method as "deduction", Holmes primarily relies on abduction: inferring an explanation for observed details.[115][116][117] "From a drop of water," he writes, "a logician could infer the possibility of an Atlantic or a Niagara without having seen or heard of one or the other."[118] However, Holmes does employ deductive reasoning as well. The detective's guiding principle, as he says in The Sign of Four, is: "When you have eliminated the impossible, whatever remains, however improbable, must be the truth."[119] Holmes follows Sir Isaac Newton's rule of "hypotheses non fingo", for instance commenting in "A Scandal in Bohemia": "It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts." Despite Holmes's remarkable reasoning abilities, Conan Doyle still paints him as fallible in this regard (this being a central theme of "The Yellow Face").[120]