How Does Sherlock Holmes Use Of Deductive Reasoning

In the first two chapters from A Study in Scarlet, Sherlock Holmes appears to employ the following four techniques (or philosophical strategies): the use of deductive reasoning, an analytical observation of details, a methodological problem-solving approach, and the use of semiotics to draw conclusions from the details he observes. All though all four of these approaches are similar in their use of details that could be construed as “signs,” they all have specific, defining qualities. Sherlock Holmes has often been described as one of the most successful users of deductive reasoning, which (in his case) involves coming to a specific, outlandish, and often correct conclusion from his observance of seemingly unimportant and minor details. In the second chapter, for example, Holmes can correctly conclude that the man who was walking down the street with a blue envelope in his hand was “the retired sergeant of Marines” by merely observing the man was “a stalwart, plainly dressed individual.” No doubt he used minor, general details about the man’s appearance that lead him to this specific conclusion. This technique is like how Dr. Michael Simms in Chapter 2 of Every Patient Tells a Story came to the specific conclusion that the patient had Lemierre’s
His use of chemicals and reliance on quantitative experiments to aid his detective work is a very specific and painstaking form of observing details to achieve a specific end. This very precise observation of quantitative and chemical details is akin to the use of quantitative data from tests performed on Maria Rogers in Chapter 1 of Every Patient Tells a Story, such as blood tests for abnormalities and liver, kidney, and other certain diseases. This chemical analysis is parallel to that done by Holmes, although his methods are more