Sherlock Holmes is sitting on his armchair in his Baker Street apartment, injecting himself with cocaine. Dr. Watson, Holmes’ assistant, remarks that Holmes has been using drugs for three times a day over the last few months. Watson feels he should try and get Holmes to stop.
Holmes’ drug use was not illegal at the time, though not without controversy (as embodied in Watson’s reaction). Holmes has clearly been using cocaine to fill a void left by the lack of a case to work on.
Watson asks Holmes why he takes drugs and risks damaging the “great powers” of his intellect. Holmes replies that his mind “rebels at stagnation.” When he doesn’t have problems to solve, he says, he longs for other means of “mental exaltation.” Holmes explains that he created a role for himself as “the only unofficial consulting detective” because it brings him great pleasure to solve problems.
Holmes himself explicitly links his drug use with his taste for problem solving—both seem to give him a similar thrill, and each precludes the requirement for the other. That is, if he has a case, he doesn’t need the drugs to fill the void. For Holmes, employing his gift for rational thinking is his very reason for being. Notably, he lacks any emotional aspect to his life.
The two men briefly discuss Watson’s write-up of one of Holmes’ recent cases; Holmes criticizes Watson for treating the subject with too much emotion and “romanticism.” Holmes then explains that a French detective has been seeking advice from him. The Frenchman is also in the process of translating Holmes’ monographs into French, on subjects like “the Distinction between the Ashes of Various Tobaccos.”
Holmes sees emotions and logic as two distinct entities—for him, there is no logic to emotions, and no emotion to logic. His mention of going beyond “romanticism” gestures towards the Victorian period’s move away from the preceding Romantic literature. Holmes’ mention of a French detective is probably a nod from Doyle to Edgar Allan Poe’s French detective, C. Auguste Dupin, and the French detective fiction writer Émile Gaboriau. Watson is established as the chronicler of Holmes’ cases, meaning everything the reader learns is filtered through him; in fact, he is in a way meant to represent the average reader.
Watson asks Holmes if there is a distinction between “observation” and “deduction,” to which he replies that there certainly is. Holmes demonstrates by explaining that he can tell Watson has visited the post office that day because he has some red earth on his shoe, which Holmes knows is from the pavement outside the post office—this is observation.
This exchange is an early taste for the reader of Holmes’ gifts. Deduction is a bit of a slippery concept in the Sherlock Holmes stories, but it is essentially a catch-all term for Holmes’ ability to go beyond observations and arrive at a given thesis or explanation for how events have unfolded.
Holmes says that, as he has been with Watson all day and not seen him write a letter, he knows that the purpose of the visit was to send a telegram—this is deduction. Holmes explains that his method is to “eliminate all other factors, and the one which remains must be the truth.”
For Holmes, then, deduction is partly about eliminating all falsehood around the truth. But he also makes use of inference—taking a set of observations and combining them to form the likeliest account of their overall cause. The main difference between him and others is that he is almost always right.
Watson proposes a further test of Holmes’ powers of deduction. He offers the other man his watch to examine. Just from looking at the watch, Holmes can tell that it used to belong to Watson’s brother, who Holmes deduces was a man who had a drinking problem.
This passage is intended to whet the reader’s appetite for the problem-solving that is to follow in the rest of the story. To the average reader, Holmes’ skillful deduction seems practically superhuman.
Watson is momentarily angered, thinking Holmes must have found out about his brother beforehand. When Holmes explains his process—which rests on observing tiny scratches on the watch, the marks of a “careless” man—Watson is in awe and apologizes. Holmes laments the fact that he has no case to work on currently: “I cannot live without brainwork.” Just then, Miss Mary Morstan arrives at the apartment.