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Aristotle, depicted here in this Roman marble bust based on a Greek original, identified logic for the first time as a separate discipline and can be called the founder of ratiocination.

conclusions (often theoretical ones) simply by observing the characteristics of the natural world.

Aristotle applied his research across a broad spectrum of topics, from physics, mathematics, astronomy, botany, and biology to ethics, the arts, and even politics. He effectively created the first coherent system of Western philosophical thought, turning each of these subjects into academic “disciplines” in their own right. Underlying Aristotle’s approach was the importance of logic, based on reasoning and derived from observation, physical evidence, empirical experiment, and general knowledge—in short, ratiocination.

The deductive and empirical process that Aristotle outlined later became central to the scientific studies of the English Franciscan friar Roger Bacon (1214–c. 1292), as well as a host of other so-called “natural philosophers” over the subsequent centuries. Observation of natural phenomena, often down to its minutiae, lay at the heart of almost all their investigations. Many were aided by contemporary inventions such as the magnifying glass, the thermometer, the telescope, and

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Forms of reasoning

Deduction Induction

Often found in classic detective fiction and Induction is a form of reasoning based on requiring incontrovertible facts, this formulaic assumptions and commonly utilized by Watson type of reasoning involves the following and the police in the Holmes stories. It requires argument: if the premises are true, then a conclusion to follow from a premise with the conclusion must also be true. probability only, rather than necessity.

Abduction Also called an “argument to the best explanation,” abduction is a form of reasoning often used by Holmes when faced with a variety of explanations for a particular occurrence. As shown below, he uses the method of abduction to help him decide which explanation best fits the evidence.

Could it be supernatural? No supporting evidence. Therefore,

Victim using

found dead abduction,

in a locked room, with no evidence Could it be a murder? No supporting evidence. the best explanation is that the

of outside victim

influence. committed

Could it be a suicide? Most likely, due to suicide.

supporting evidence.

the microscope, all of which permitted them to delve ever deeper into their respective observations and discoveries; Holmes also uses these tools.

The science of deduction

By the time Conan Doyle began writing the Holmes stories in the 1880s, Aristotelian thought and the philosopher’s demonstrations of empirical logic had become central to most educational and scientific systems in Western culture. Ratiocination defines Holmes’s principal approach to a problem—that is, deduction based on the evidence available; however, Holmes also uses variants of detection and logical thought that often place him several steps ahead of the regular, plodding, do-it-by-the-book police investigators.

“Inductive” reasoning, for example, is a technique used in mathematics and chemistry (in which Holmes was trained), whereby a theoretical inference might be reached based purely upon the particular circumstances of an experiment or situation that itself stands outside “received” knowledge. While Holmes does take this approach, it is also often colored by his perception of the protagonists involved. In The Valley of Fear (pp.212–21), for example, Holmes finally reduces the mystery to an inevitable conclusion through a process of weighing up possible solutions alongside his perception of the protagonists’ characters.

However, more often Holmes uses “abductive” reasoning—quite literally the removal of a person or, in Holmes’s case, an idea, from the potential scenario of a crime, thereby leaving the theoretical question “What if…?”. He uses this to good effect in “The Man with the Twisted Lip” (pp.80–1), when he “abducts” that Neville St. Clair, who has apparently disappeared, in fact never left the room that he was ❯❯

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last seen entering. All that is found in the room are his clothes and an old beggar man. In asking the question, “What if he never left?” Holmes can abduct that the beggar man is, in fact, St. Clair in disguise.

The deployment of the method of ratiocination in crime-solving was not invented by Conan Doyle— he was building on a fictional tradition that originated in the “murder mystery” tales created by the American writer Edgar Allan Poe (1809–1849), whose interests stretched from contemporary science to cryptanalysis (the study of ciphers)and the supernatural. Poe published a trio of short stories featuring the detective C Auguste Dupin. In all three tales, Dupin uses the devices of ratiocination to solve murders, observing the evidence

Edgar Allan Poe, whose fictional detective Dupin is shown here in this illustration from “The Purloined Letter” (1844), was an early proponent of ratiocination in his stories.

and often projecting himself into the mind of the criminal before reaching a damning conclusion. Subsequent writers, such as Wilkie Collins and even Charles Dickens, picked up on this theme, although not with the ferocious enthusiasm of Conan Doyle who, through the character of Holmes, strengthened the concept of ratiocination in his absolute reduction of logic to an essential conclusion.

A well-stocked brain attic

Conan Doyle’s presentation of his detective as a fundamentally scientific individual and a pioneer of forensic crime-solving methods (Watson first meets Holmes when the latter is a medical research chemist at St. Bartholomew’s Hospital in London) is telling—it is a scenario that provides the key to most of the Holmes mysteries.

However, in the first Holmes novel, A Study in Scarlet (pp.36–45), Conan Doyle sets some interesting limitations on the great intellectual powers of his eccentric and brilliant sleuth. As he gets to know his enigmatic new companion, Watson notes that Holmes is astonishingly selective in what he chooses to learn: he knows nothing about literature, philosophy, astronomy, or politics, yet has a deep understanding of chemistry, an encyclopedic knowledge of “sensational literature” (accounts of criminal cases), and a “practical knowledge” of British law. Holmes brushes this implied criticism aside, stating that he is only interested in that which will prove useful to him in his work. “I consider that a man’s

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brain originally is like a little empty attic, and you have to stock it with such furniture as you choose,” he tells Watson. He is careful to fill his own “brain attic” with facts and information that he can draw on to make his deductions and solve cases—at the expense of other things he considers superfluous, even fundamental truths about science and the universe. “There comes a time when for every addition of knowledge you forget something you knew before,” Holmes explains.

“The observance of trifles”

Further revelations about Holmes’s methodology are gradually revealed over the ensuing 40 years, in the stories that follow A Study in Scarlet. Conan Doyle focuses on the small, detailed, but outstanding and often overlooked features of a crime, which provide Holmes with the key to many apparently unsolvable riddles, much to the astonishment of Watson. It is not only cold, hard logic but also Holmes’s highly developed eye for detail that enables him to solve crimes: “I can never bring you to realize the importance of sleeves,

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.

Galileo Galilei

(1564–1642)

the suggestiveness of thumb-nails, or the great issues that may hang from a bootlace,” he remarks in “A Case of Identity” (pp.68–9).

Equally significant is Holmes’s shrewd, encyclopedic knowledge of seemingly arcane data: the impressions left by a carriage, bicycle tires, or footprints; the myriad types of tobacco ash found at a scene in an era when almost every man smoked; the tiny clues offered up by dirt and dust particles—all of which provide extra information for him when solving cases. Holmes

Darwin and ratiocination

Charles Darwin’s groundbreaking book On the Origin of Species (1859), perhaps the most influential scientific treatise of the 19th century, used ratiocination to devastating effect. In this detailed publication, Darwin (1809–1882) propounded his concepts of a theory of natural selection, the “survival of the fittest,” and from there to his general theory of evolution. A prime example of Aristotelian logic and deduction, the work sparked global debate and sold out on publication day.

regularly consults his obsessively compiled “great book,” into which he pastes daily clippings of the agony columns (personal advertisements) of popular newspapers. These were often used as a means of disguised or coded communication and, according to Holmes, were “the most valuable hunting ground that ever was given to the student of the unusual.”

A lasting impact

The Holmes stories incorporate several historic developments: a flood of new research was rapidly entering into everyday life and the popular consciousness—which the detective eagerly exploits— while police practices were also gradually becoming more scientific and rigorous. An entirely new way of looking at the human personality, psychoanalysis, was also becoming popular, although it is difficult to prove the extent to which Sigmund Freud’s work influenced Conan Doyle’s writing. However, it was with Holmes’s methods of deduction that Conan Doyle introduced a new scientific rigor to the mystery story that would impact crime writing for over a century to come. ■

Many of Darwin’s crucial premises were derived from seemingly arcane and very small clues—accumulated over many years from his studies of fossils, geology, and animal and bird behavior. His conclusions often flew in the face of received knowledge, tradition, and prejudice. In Conan Doyle’s Sherlock Holmes stories, the great detective stands squarely within this tradition, although he has to move quickly to track down the perpetrators of crime.

THERE IS

NOTHING LIKE

FIRST-HAND

EVIDENCE

CRIMINOLOGY AND FORENSIC SCIENCE

C

riminology and forensic science as we know them emerged in the 19th century, and had become well-established in criminal investigations by the turn of the 20th century. However, their origins lay in the 18th century, when there was great scientific progress in the fields of chemistry, physics, botany, zoology, geology, and anatomy. This increase in scientific knowledge led to a more rational, non-speculative, evidence-based approach to solving crimes, and opened up a wider field of possibilities for the police. Conan Doyle made Sherlock Holmes a pioneer of forensic analysis and the use of reasoning, and as a detective working in the 19th century he was in many ways ahead of his time.

The main contributors to the development of criminology as a science were German psychologist and neuroanatomist Franz Josef Gall (1758–1828) and the Italian

Reformer and politician Sir Robert Peel (1788–1850) created the first British police force. The policemen were called peelers or bobbies (after Peel’s nickname “Bob”), a term still in use today.

CRIMINOLOGY AND FORENSIC SCIENCE 311

sociologists Cesare Beccaria (1738–1794) and Cesare Lombroso (1835–1909). Beccaria published On Crimes and Punishments (1764), in which he argued that crime was an endemic trait of human nature; Lombroso rejected this idea, claiming that psychological, social, and inherited conditions predisposed a person toward criminal tendencies.

Urban expansion and crime

Rapid population growth and urbanization at the end of the 18th century—especially in London, Manchester, Liverpool, Edinburgh, and Glasgow, as well as many other industrial cities across Europe (particularly Paris)—presented new social challenges. Urban expansion created dense populations within which crimes could be concealed easily and criminals could move around unnoticed in the crowds. This meant that policing, crime control, and solving or resolving criminal cases of forgery, assault, burglary, homicide, and organized gang crime became pressing issues. Previously, crimes had been dealt with on a largely local basis, within small communities, based on local knowledge and relatively simple information-gathering. However, this often involved rumor, hearsay, or prejudice—hence, in part, the so-called “witch trials” of the 16th and 17th centuries, in which local scores were settled by invidious accusations.

The first professional police forces set up to investigate crimes came into existence in the early 19th century. In 1812, Eugène François Vidocq (see p.317), a former criminal, established the Sûreté Nationale in Paris; it was a modest but ambitious operation that recruited other reformed criminals to its staff. In 1829, Robert Peel set up the Metropolitan Police Service, based at Scotland Yard in Whitehall, London, in

The Watch House in London’s Covent Garden was built in 1729. In 1829, the newly formed Metropolitan Police took it over as headquarters of F Division, controlled by Superintendent Thomas.

consultation with Vidocq. It would be many years later that the burgeoning population of the US saw the creation of the Bureau of Investigation in 1908 and its cross-state federal remit, the Federal Bureau of Investigation (FBI), which was introduced in 1935 under its first director,

J. Edgar Hoover. The aim of these policing institutions was to centralize information-gathering and intelligence distribution on a national and even transnational basis. The International Criminal Police Organization (Interpol) was another French innovation, created in 1923 to share and disseminate information around the world.

In addition to a new style of policing, a different dimension of detection and crime resolution became necessary, using a range of new techniques and methodologies. The principal steps forward in this area during the 19th century (of which Conan Doyle was well aware) fell into three main categories: the gathering of intelligence, especially concerning the activities of the ❯❯

Police are the public and the public are the police.

Sir Robert Peel

“Principles of Policing” (1829)

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“underground” classes; the collection and collation of details and characteristics of criminal “types” (phrenology and anthropometry); and the scientific analysis of forensic material gathered at the scene of the crime—unique datasets such as fingerprints, photographic files, and traces of blood types. A fourth important element was the development of a range of new infrastructure systems: the popular press, railroads, an efficient postal service, and high-speed communications, especially the telegraph—all of which Holmes exploits extensively in solving the enigmas that confront him.