Sherlock Holmes and Philosophy

by Josef Steiff

  Unfortunately for us, Holmes never had time to write this textbook. And we don’t know for sure what he would have written, but we can follow up some clues from his cases.

  Asking the Right Question

  Sherlock Holmes called his method by many names. It was the “Science of Deduction and Analysis” or simply “Science of Deduction” which demands faculties of observation, and deduction, as well as knowledge on relevant areas of life. It required “curious analytic reasoning from effects to causes”. It demanded faculties of deduction and logical synthesis; or analysis.

  Jaakko Hintikka, a philosophical Sherlock in his own right, has maintained that Holmes’s secret was the skillful use of the old Socratic method: in uniting the art of reasoning with the art of providing proper questions and answers. Other Socratics (like Matti Sintonen) have agreed. Holmes is able to find key issues in problematic situations by framing strategically useful questions. For example, in “Silver Blaze” the key question is the odd behavior, or actually the lack of behavior, of the dog during the robbery of the famous racing horse Silver Blaze:

  “Is there any other point to which you would wish to draw my attention?”

  ‘To the curious incident of the dog in the night-time.”

  “The dog did nothing in the night-time.”

  “That was the curious incident,” remarked Sherlock Holmes.

  Did the dog bark? No. Why does a watchdog not bark in the middle of the night, if something odd is happening? Because whatever was happening in the night-time, the perpetrator must have been somebody the dog knew well enough not to be disturbed by him.

  As with many great discoveries, Holmes’s questions seem self-evident after the discovery has been made. But as with many discoveries, coming up with the right questions beforehand is a very tricky task. Good questions are just those questions by which you eventually solve your case. But it takes a Sherlock Holmes, or Holmes’s methods, to come up with such questions.

  Playing the Guessing Game

  Holmes’s reasoning does not only rely on knowing the definitional rules of logic. It’s about coming up with chains of arguments which support the search for key issues in the case. It’s more about having a good strategy for reasoning than about reasoning as such. As Hintikka has emphasized, the master player in games of chess is not the one who knows the basic rules of the game extremely well, but the one who is a master in the strategies and heuristics of the game. The same applies to the art of detection and reasoning.

  It’s often been claimed that Holmes’s method was not, in fact, deduction, but abduction. Charles Peirce, the famous American philosopher and logician, maintained that reasoning falls into three categories.

  ● Deduction, the pattern of reasoning by clarifying logical necessities.

  ● Induction, reasoning on the basis of what “actually is.”

  Induction has attracted philosophers’ minds for ages. We use various kinds of inductive reasoning all the time, for instance, when making generalizations. According to Peirce, there is, however, also another form of non-deductive reasoning: abduction.

  ● Abduction, the main kind of reasoning we use for coming up with new ideas.

  Abduction is weaker than induction. And it is much more speculative than deduction. Abduction is about crafting hypotheses and fertile possibilities on the basis of clues. Abduction is used when we look for possible explanations for somehow surprising events. Even if abduction is weak as a form of reasoning (it’s about maybe’s) it’s strong and useful where discoveries and novelties are concerned. When we aim at inventing something new we cannot deduce it by necessity or inductively generalize it from existing knowledge. We need ways of inventing and developing new possibilities.

  Despite being a fan of Edgar Allan Poe, the grand old man of the detective genre, Peirce himself did not make a strong connection between abduction and detective work. Others, such as Thomas A. Sebeok, Jean Umiker-Sebeok, and Umberto Eco have, however, noticed how Sherlock Holmes’s work is often like abductive reasoning. Typically, abduction is about reasoning “backwards” from consequences to causes or explanations. When a murder has happened, various signs are left at the crime scene that tell us something about the crime and the perpetrator. Abduction is coming up with explanations for these signs.

  Reasoning backwards is what Sherlock Holmes calls “analytic,” as opposed to “synthetic” reasoning. Synthetic reasoning is asking: What happens next? Analytic reasoning is asking: How did this come about?

  “In solving a problem of this sort, the grand thing is to be able to reason backward. . . . In the everyday affairs of life it is more useful to reason forward, and so the other comes to be neglected. There are fifty who can reason synthetically for one who can reason analytically.” (A Study in Scarlet)

  We know the end result. The trick is to use this knowledge for inventing novel hypotheses about how the result came about.

  Holmes is always making detailed observations and minute investigations at the crime scene in order to provide materials to start these backward reasonings. Abductive reasoners especially look for strange happenings and little details that don’t quite fit, as clues when searching for potential explanations. As Sherlock Holmes says in “The Boscombe Valley Mystery”: “You know my method. It is founded upon the observation of trifles.”

  Details and strange happenings can be used as a starting point for providing logically elegant solutions and chains of reasoning. These details can be so small that at one extreme abductions turn on hints which we’re not even aware of. Nonetheless, they can help when guessing and searching candidate solutions.

  Abduction is not, however, just wild, intuitive guesswork. While the process of discovery might begin with intuitively forming a hypothesis, such a hypothesis is in the end strengthened in a very Sherlockian manner: by drawing deductive inferences that coincide with the known facts.

  Maybes and Must Bes

  The beginning phases of Holmes’s abductive process involve minute observation, guesswork, and imagination. Holmes can craft several possible scenarios that could be used to crack a given conundrum. He does not, however, commit to any single one before he had enough information to settle on a single hypothesis:

  “I have devised seven separate explanations, each of which would cover the facts as far as we know them. But which of these is correct can only be determined by the fresh information which we shall no doubt find waiting for us.” (“The Adventure of the Copper Beeches”)

  Holmes also holds that imagination has a key role in drawing his impressive inferences:

  “See the value of imagination. . . . It is the one quality which Gregory lacks. We imagined what might have happened, acted upon the supposition, and find ourselves justified.” (“Silver Blaze”)

  While observation, guesswork, and imagination are central to abduction, this peculiar mode of inference involves more than just guessing. Indeed, Sherlock himself objected to plain guesswork in The Sign of the Four: “I never guess. It is a shocking habit—destructive to the logical faculty.”

  Abduction is not pure guesswork but is based on skillful use of clues and constraints. Guesswork and imagination function as the first stage of discovery. The ingenuity of Holmes’s method is combining the imaginative capacity with impressive skills in all forms of inference. Holmes firmly objects to speculations on their own. Only once data has been gathered can we draw up a hypothesis: “It is a capital mistake to theorize before you have all the evidence. It biases the judgment” (A Study in Scarlet).

  Good abductive “guesses” need some material. The inquirer uses clues, previous knowledge, and new observations to trigger and guide guesses. These speculations must then be checked separately. This is not traditional inductive methodology where data is simply compiled together in order to reach more general truths. Rather, data provides triggers for searching explanations and novel perspectives.

  While the grounds for abductive reasoning can be based on drawing hypotheses on the b
asis of clues, the whole process of reasoning also involves deduction and induction. New premises are introduced by anticipating how to draw deductions from them. If the deductions are verified by novel observations, the hypothesis is strengthened, otherwise not. The inquiry process requires three processes of reasoning: abduction, deduction, and induction.

  A clear example of the process of Holmes’s combining abduction with deduction and induction can be found in the classic encounter of Holmes and Watson near the beginning of A Study in Scarlet. When he first meets Watson, Holmes quickly concludes that Watson has been in Afghanistan. Later Sherlock explains this to Watson:

  “The train of reasoning ran, ‘Here is a gentleman of a medical type, but with the air of a military man. Clearly an army doctor, then. . . .’”

  The start of this train of reasoning is then more like detailed observation.

  “He has just come from the tropics, for his face is dark, and that is not the natural tint of his skin, for his wrists are fair. . . .”

  This is an abductive explanation for the darkness of the face, which is clearly not Watson’s natural tint (on the basis of a clue concerning his wrists).

  “He has undergone hardship and sickness, as his haggard face says clearly. His left arm has been injured. He holds it in a stiff and unnatural manner. Where in the tropics could an English army doctor have seen much hardship and got his arm wounded? Clearly in Afghanistan.”

  An abductive explanation for various clues and observations (injured arm, coming from tropics, army doctor) pointed with a key question.

  “The whole train of thought did not occupy a second. I then remarked that you came from Afghanistan, and you were astonished.”

  And then, if needed, from the hypothesis that Watson is an injured army doctor who has just come from Afghanistan, supported by some additional, commonplace suppositions, all details can be deduced and the whole thing checked inductively.

  Three to Get Ready

  Besides abduction there is another Peircean idea which illuminates Sherlock Holmes’s methods.

  Peirce founded his famous theory of signs on an elegantly simple idea of three basic categories: Firstness, Secondness, and Thirdness. These categories appear in many forms. As metaphysical categories, firstnesses are things in themselves. Good examples are qualities of feeling, possibilities and icons. Secondnesses are two things clashing against each other, such as reactions, actualities and indices. Thirdnesses concern mediation, where some things are brought together with mediating processes which is more complicated than just two things reacting with each other, such as rules, symbols and reasoning.

  Even though they are categories, the strength of firstnesses, secondnesses, and thirdnesses comes from combinations and mixtures. For example, abduction is a form of reasoning. Therefore it is about mediation and Thirdness. But its peculiarity comes from using tones, potentialities, iconic resemblances—firstnesses—as a fuel for reasoning: the clues and elements from which the abductive hypotheses are formed.

  An important part of Holmes’s methods is that he is so good at combining in his work the different Peircean categories: qualities of feeling and imagination, actions and reactions, and different forms of reasoning. It’s more typical to be good at one of these areas, or maybe at two of them. Holmes is a Peircean savant: an expert in all three categories. Although Holmes doesn’t always want to admit it, reasoning includes an element of the dream (especially through abductions) and action (with inductions). Peircean categories work for each other.

  Most famously, Sherlock Holmes is uncanny in drawing inference, and he often emphasizes their exact and “scientific” nature. “Detection is, or ought to be, an exact science and should be treated in the same cold and unemotional manner” (The Sign of the Four).

  Holmes could solve some easier cases just by armchair reasoning. But he’s also a man of action. This takes several forms. He is a true forerunner of crime scene investigation with the use of various instruments like a magnifying glass or a tape measure to get the evidence he needs, instead of relying only on what can be seen by the naked eye.

  Holmes is keen on making experiments which help him to analyze evidence, like making a test for blood stains, or distinguishing differences in cigar ashes. These kinds of experiments were complemented by his detailed knowledge of crimes and horrors perpetrated down the centuries, which he refers to while searching for apparent novelties. “There is nothing new under the sun. It has all been done before” (A Study in Scarlet).

  An expert fighter, Sherlock doesn’t hesitate to put his fists up and his neck on the line if a case requires it. He’s always ready, with Watson, to risk his own life and well-being when grappling with the London underworld. He goes to enormous trouble to find crucial pieces of evidence, sometimes using disguise to elicit information. “‘They say that genius is an infinite capacity for taking pains’, he remarked with a smile. ‘It’s a very bad definition, but it does apply to detective work’” (A Study in Scarlet).

  Finally, in addition to being a man of reason and a man of action, Sherlock is also a man of imagination and daydreaming. Watson notes in “The Copper Beeches,” “As to Holmes, I observed that he sat frequently for half an hour on end, with knitted brows and an abstracted air.”

  His toolbox did not consist only of his wit, his scientific equipment and his fists, but just as much of his violin and his armchair which he would use to feed his reasoning and to make room for novel insights while pondering the cases. While these elements of his character would sometimes backfire, as was arguably the case with his addiction to intravenous cocaine, the element of reverie was just as central to Sherlock’s methodology as was his colder reasoning capacity, or his skills in the field.

  Peirce once remarked that there are three classes of human beings related to three categories: those to whom the chief thing is the qualities of feeling and art, secondly the practical men, and thirdly those who emphasize thinking. Sherlock Holmes manages to combine all of these features to serve his methods.

  Holmes’s methodology covers the entire process of discovery. First, he provides the clay of thought by the way of minute observation and related imagination and reverie. Secondly, his meticulous capacity for chains of reasoning provides the forms into which the clay is molded. And finally, as a man of action, he is also capable of working with the bricks themselves when needed to get constructions ready, or to get more clay for thought. By being a sovereign master of all Peircean categories, the master sleuth is a superb renaissance man. However, this is not because he has somehow magically been endowed with such skill. Quite the opposite, the secret of Sherlock Holmes’s detection lies, as he so often emphasizes, in his methods and the practical skills for mastering them.

  A Toolbox for Your Holmes

  Sherlock Holmes maintains that although his methods seem to be theoretical they are “extremely practical” as well. Here’s a short toolkit of Holmes’s methods. The list is by no means exhaustive, but gives some advice for those interested in effective methods:

  ● Formulate the problem you set out to solve clearly and distinctly.

  ● Observe and make experiments: investigate carefully your area of interest.

  ● Pay attention, especially to surprising details and clues: keep your focus on the concrete but what is easily evanescent.

  ● Keep yourself up to date and focus your work: build an extensive library and index of relevant information.

  ● Theorize, but by taking facts into account: create hypotheses that are viable in terms of the data.

  ● Don’t be satisfied with half-baked explanations: do not give up before you have solved the mysteries.

  ● Aim at elegant chains of logical connections: Even the most intricate tangle of things can be sorted out with dedicated inquiry.

  ● Ask specific questions: by formulating questions you can narrow down the applicable data and theories.

  ● Refine the tools and instruments needed in your work: Good work requi
res good tools, and advanced practice in using these tools.

  ● Test and retest: your favorite ideas can turn out to be wrong or biased.

  ● Surround yourself with people who can help you in various tasks needed in your work: Not even Sherlock Holmes can work alone.

  ● Get involved! Do only those things that really make sense for you and what you love most.

  We can’t claim to have unveiled all the secrets of Holmes’s methods. Like any art or expertise, learning these methods requires practice and long and patient study. It is not a question of inborn capacities but a result of practice. There will always, no doubt, remain a shroud of mystery around the mastery of the Baker Street detective’s methods.

  Furthermore, the methods of detection have in some senses changed dramatically during the last hundred or so years. Therefore, modern Holmeses need even more elaborate methodologies, techniques, and collaboration for problem solving than was the case in Holmes’s day. Nonetheless, making observations, asking questions, using all forms of reasoning, and combining aspects of imagination, action, and intelligence, will no doubt remain some of the most useful tools for people involved in any line of detection.