Watson narrates that he and Holmes were pleased with their new rooms and living arrangement. Holmes was not difficult to live with, as he had regular hours and was often out. He did have occasional bouts of lethargy and immobility, which Watson believed were not related to drugs because of the man's "temperance and cleanliness."
Watson was incredibly interested in Holmes and his mysterious doings; he had a copious amount of free time while regaining his health as well as a lack of friends in London to occupy his time. Holmes was clearly not studying medicine, Watson concluded, and he was not perusing any other degree. His knowledge seemed exact and desultory, focused on several small things and amazingly lacking in others. In particular, Watson was shocked that Holmes had never heard of the Copernican discovery of Earth's revolutions around the sun; Holmes responded that this was because "it is of the highest importance...not to have useless facts elbowing out the useful ones."
At one point, Watson took up a pen and wrote a list of the different types of knowledge and marked which ones Holmes seemed conversant in. He knew little to nothing of literature, philosophy, astronomy, and politics. He had a practical but limited understanding of geography, a variable understanding of botany, a profound knowledge of chemistry, an accurate but unsystematic knowledge of anatomy, and an immense knowledge of sensational literature. Holmes was quite talented on the violin, and seemed to play pieces of music that reflected his current thoughts, whether gloomy or excited.
Watson believed Holmes to have no friends when they first began their cohabitation, but soon noticed various individuals from different classes of society visiting him. Holmes explained that they were his clients but offered no further information.
One morning while Watson was waiting for his breakfast he picked up a magazine from the table and glanced at an article called "The Book of Life." This article attempted to explain "how much an observant man might learn by an accurate and systematic examination of everything that came in his way." A man could look at a drop of water and know what ocean it came from, or learn a man's calling from his fingernails or coat-sleeve. Watson scoffed that this article was "ineffable twaddle" and threw it upon the table. He complained to Holmes, who sat across from him, that the article was irritating and impractical.
Holmes listened to Watson and then told him that he was in fact the author of the article and that his job was a "consulting detective." This, in essence, meant that he was a private detective and he endeavored to help government detectives sort out their evidence in crimes. Those clients he mentioned were people who came to him to ask for "enlightening" on some problem they had. For more complex cases, Holmes would visit the site itself and apply his specialized knowledge and powers of observation. To make this clearer, he explained to Watson how, upon their first meeting, he had known Watson was just from Afghanistan.
Watson was surprised at these revelations and commented that Holmes reminded him of Edgar Allen Poe's Dupin and Gaboriau's detective Lecoq. Holmes was disdainful of these comparisons, not finding them accurate enough or indicative of his own talents. He then began to complain that he never got to work on any real cases as there were no crimes being committed.
Watson, becoming annoyed at Holmes’ "bumptious style of conversation," changed the topic to wondering who a man on the street below was looking for. Holmes glanced at the man and said that he was a retired sergeant of Marines. Watson was skeptical at this instantaneous assessment, but had little time to consider it further because the man on the street came up to their very door. Upon it being opened, the man handed Holmes a letter. Before he left Watson asked him his profession, and to his amazement the man answered that he was a sergeant from the Royal Marine Light Infantry.
In this chapter more of Holmes’ eccentricities and idiosyncrasies are presented to Watson and the reader. His areas of expertise are fascinating in their diversity, and the areas of knowledge where he knows little to nothing are rather surprising. The theory that Holmes is a drug user also comes to the fore, with Watson initially speculating as to whether or not Holmes’ moods indicated drug usage and then finally rejecting that hypothesis as being unrealistic given Holmes’ character. Holmes also delves into his method of working and clears up the minor mystery of how he was able to tell that Watson had been in Afghanistan. The essence, it is clear, of Holmes’ methodology is extreme observation and deductive reasoning.
This deductive reasoning makes Holmes a fantastic "consulting detective," as he labels himself. A Study in Scarlet is a riveting detective story, and one of the first and best of its kind. In fact, many scholars point to its place as the first major detective novel. As literary scholar Frank McConnell points out, "every detective story written since Scarlet stands in its shadow." Although Doyle was somewhat of a minor talent- some of the story is clumsily written and the prose unremarkable –he created something that has been profoundly influential for over a century.
McConnell sees several reasons for this. One, he explains, is the fact that Doyle was quite vulnerable to the modes of thought of his time and born into a remarkable and interesting age. The hallmarks of 20th-century life were born here –slums, suburbs, unemployment, economic turmoil, psychological problems, tensions between tradition and modernity, etc. Modern crime was exemplified by the terrifying, anonymous Jack the Ripper killings. Thus, Arthur Conan Doyle "was found by an audience inhabiting a city too large to be understood, frightened by a half-understood scientific proof that seemed to some to suggest that we all shouldn't be here anyway. Doyle's was a society, moreover, that would soon be terrorized by the realization that, in a world where all is possible, all is possible." Also, this time period featured growing literacy amongst a group of people from the lower classes who thrilled to these types of tales.
The Holmes stories have spawned many culturally significant and recognizable imitators from Philip Marlowe to James Bond, and the structure of the detective story is "in the mode of play, the structure of the very age that gives it birth, the age of analysis, linguistic, Freudian, or physical." All of the famous detectives in cultural history feature men standing outside the known universe, committed to analysis of said universe and trying to uncover its order through analysis.
McConnell explains that this evocation of pure reason is crucial to the detective story genre, but that "the detective story is not really about the power of reason, but rather about the myth of reason, about the desperately hoped-for chance that the universe might be comprehensible..." This is no doubt why the Holmes tales were so popular in their day, and why they, along with other detective stories, remain appealing and comforting.