2. Sherlock Holmes – Method and Character

2.1. Characteristic Elements of the ‘Method of Deduction’

A survey of Sherlock Holmes’ scientifically oriented working method: from observations to conclusions. With examples from selected original stories by A.C. Doyle.

Sherlock Holmes – the mere name is usually enough to conjure the picture of a benevolent genius, who by his extraordinary powers of reasoning manages to discover what anyone else failed to see and hardly ever looses in his struggle for the truth.
Although this is not exactly the image Conan Doyle presents of the detective, the extraordinary Method of Deduction Holmes has come to symbolise alongside with his unique gifts and traits are undoubtedly at the heart of the Canon.
What, then, does this method consist of?

Holmes’ working method entirely rests on data. His primary sources of information are the clients’ accounts, which he usually clarifies by asking the right questions, and the knowledge he obtains analysing his own minute observations.
Interpreting apparently marginal details with his characteristic skill, he is able to read the appearance of a person or a commonplace object with perfection and discover infinitesimal facts that otherwise would have gone unnoticed.
In this context, Sherlock Holmes repeatedly emphasises that ‘observing’ means far more than just glancing at an object or even spotting the correct items.
Each detail must actually register on the observer’s mind to be of use:

“[…] The distinction is clear. For example, you have frequently seen the steps which lead up from the hall to this room.” –
“Frequently.” […] –
“Then how many are there?” –
“How many? I don’t know.”
“Quite so! You have not observed. And yet you have seen. That is just my point. Now, I know that there are seventeen steps, because I have both seen and observed.” (from: “A Scandal in Bohemia”)

Once gathered, this information about the present is used to derive from it the chain of events that led to the crisis at hand: Working on the assumption that practically everything that occurs – however queer it may seem in itself – is the logical consequence of earlier incidences, which left visible traces, the detective analyses the present state of things carefully and deduces its history, explaining the client’s case on the basis of cause and effect.

Holmes – or rather Conan Doyle – rightly remarks that this kind of thinking is in a way the counterpart to the logic we usually apply. Whereas in everyday- life we use our mind to predict future developments from the facts available at present, Sherlock Holmes does “backward reasoning”  to learn about the past.
In my opinion, this is one of the reasons why this approach to a problem gives a rather convincing and realistic impression – whether it may be of any practical use in our non-fictional world remains open to debate, of course.
As the gift of ”analytical reasoning” is very rare (1), even if it might well be acquired by patient training, it makes the detective superior to most of his opponents and enables him to see clearly about mysteries that seem absolutely inexplicable to others(2).
The extent of knowledge he is thus able to gain at great ease “baffles” not only clients, colleagues or criminals but – first and foremost – the reader:

“ […] How do I know that you have been getting yourself very wet lately, and that you have a most clumsy and careless servant girl?” –
“My dear Holmes,” said I, "this is too much. […] It is true that I had a country walk on Thursday and came home in a dreadful mess […]. As to Mary Jane, she is incorrigible, […] but there, again, I fail to see how you work it out.”
He chuckled to himself […]: “It is simplicity itself,” said he; “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.
(from: “A Scandal in Bohemia”)

This extract from the first Sherlockian short story exemplifies precisely the extraordinary ability most people implicitly associate with the detective(3).
As it is based on nothing but ‘objective reality’, the Method of Deduction – almost inevitably – leads to the truth, since once “you have eliminated the impossible, whatever remains, however improbable, must be the truth.”(4).

To reach this high aim, it is of course essential for the investigator to work flawlessly, which in Holmes’ case means basically two things: First of all, he generally avoids forming an opinion in advance, which is necessary, as otherwise “one [insensibly] begins to twist facts to suit theories, instead of theories to suit facts. ”(5). Furthermore, he usually checks individual facts and each solution he has come up with, to ensure its reliability. This link between the outside world and his theories is indeed very important to the detective.
In fact, Holmes often takes far more practical action then the detection of a crime itself would require: once he has come to a profound conclusion, he uses his ratio as well as his consciousness to decide what is to be done. As a rule, he does not hesitate to assist a client himself or – if necessary – fight a criminal by force.
He thus combines both, practical and theoretical skill on a high level – both of which dominate his personality.