Sherlock Holmes on Problem Solving


Gregg Young, the author of the book, Reasoning Backward: How Sherlock Can Make You a Better Problem Solver, has suggested the following list of 70 Sherlock Holmes quotes from the Sherlock Holmes canon. Many of these quotes will be appearing in the next edition of Reasoning Backward: How Sherlock Holmes Can Make You a Better Problem Solver. Gregg Young is the President of Young Associates, Inc. For more information about Gregg Young, go to Young Associates, Inc.

To order the book, go to Reasoning Backward: How Sherlock Holmes Can Make You a Better Problem Solver

Reason backward…

“What is out of the common is usually a guide rather than a hindrance. In solving a problem of this sort, the grand thing is to be able to reason backward. That is a very useful accomplishment, and a very easy one, but people do not practice it much. 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 … Most people, if you describe a train of events to them, will tell you what the result would be. They can put those events together in their minds, and argue from them that something will come to pass. There are few people however, who, if you told them a result, would be able to evolve from their own inner consciousness what the steps were which led up to that result. This power is what I mean when I talk of reasoning backward, or analytically.” – A Study in Scarlet 

“The ideal reasoner would, when he had once been shown a single fact in all its bearings, deduce from it not only all the chain of events which led up to it but also all the results which would follow from it. As Cuvier could correctly describe a whole animal by the contemplation of a single bone, so the observer who has thoroughly understood one link in a series of incidents should be able to accurately state all the other ones, both before and after.” – The Five Orange Pips

“The case is one where we have been compelled to reason backward from effects to causes.” – The Adventure of the Cardboard Box

“It is not really difficult to construct a series of inferences, each dependent upon its predecessor and each simple in itself. After doing so, one may produce a startling effect.” – The Adventure of the Dancing Men

“Some facts should be suppressed, or, at least, a just sense of proportion should be observed in treating them. The only point in the case which deserved mention was the curious analytical reasoning from effects to causes, by which I succeeded in unraveling it.” – The Sign of Four

“Yes, I have a turn both for observation and for deduction. The theories which I have expressed there, and which appear to you to be so chimerical, are really extremely practical — so practical that I depend upon them for my bread and cheese.” –A Study in Scarlet

“Is it beyond the limits of human ingenuity to furnish an explanation which would cover both these big facts? If it were one which would also admit of the mysterious note with its very curious phraseology, why, then it would be worth accepting as a temporary hypothesis. If the fresh facts which come to our knowledge all fit themselves into the scheme, then our hypothesis may gradually become a solution.” – The Adventure of Wisteria Lodge

“You’re like a surgeon who wants every symptom before he can give a diagnosis.” “Exactly,” Holmes responded, “That expresses it. And it is only a patient who has an object in deceiving his surgeon who would conceal the facts of his case.” The Problem of Thor Bridge 

Eliminate the impossible… 

“When you have eliminated the impossible, whatever remains, no matter how improbable, must be the truth.” – The Sign of Four

“We must fall back upon the old axiom that when all other contingencies fail, whatever remains, however improbable, must be the truth.” – The Adventure of the Bruce-Partington Plans

“Eliminate all other factors, and the one which remains must be the truth.” – The Sign of Four

“How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth?” – The Sign of Four

“The process starts upon the supposition that when you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth. It may be that several explanations remain, in which case one tries test after test until one or other of them has a convincing amount of support.” –The Adventure of the Blanched Soldier

“When you follow two separate chains of thought, Watson, you will find some point of intersection which should approximate to the truth.” – The Disappearance of Lady Frances Carfax

“Any truth is better than indefinite doubt.” – The Yellow Face

Begin with a blank mind… 

“Always approach a case with an absolutely blank mind. It is always an advantage. Form no theories, just simply observe and draw inferences from your observations.”     – The Adventure of the Cardboard Box  

“We approached the case, you remember, with an absolutely blank mind, which is always an advantage. We had formed no theories. We were simply there to observe and to draw inferences from our observations.” – The Adventure of the Cardboard Box

“I make a point of never having any prejudices, and of following docilely wherever fact may lead me.” – The Reigate Puzzle

“I will not bias your mind by suggesting theories or suspicions, Watson. I wish you simply to report facts in the fullest possible manner to me, and you can leave me to do the theorizing.” – The Hound of the Baskervilles

“To the logician all things should be seen exactly as they are.” – The Greek Interpreter

“Detection is, or ought to be, an exact science, and should be treated in the same cold and unemotional manner. You have attempted to tinge it with romanticism, which produces much the same effect as if you worked a love story or an elopement into the fifth proposition of Euclid.” – The Sign of Four

“The emotional qualities are antagonistic to clear reasoning.” –The Sign of Four 

“It is of the first importance not to allow your judgment to be biased by personal qualities. Emotional qualities are antagonistic to clear reasoning.” – The Sign of Four 

Observe first to gather data… 

“It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” – A Scandal in Bohemia 

“It is an error to argue in front of your data. You find yourself insensibly twisting them round to fit your theories.” – The Adventure of Wisteria Lodge

“It is a capital mistake to theorize before you have all the evidence. It biases the judgment.” – A Study in Scarlet

“ It is a capital mistake to theorize in advance of the facts.” –The Adventure of the Second Stain

“To let the brain work without sufficient material is like racing an engine. It racks itself to pieces. … Let us get a firm grip of the very little which do know, so that when fresh facts arise we may be ready to fit them into their places.” – The Adventure of the Devil’s Foot

“How dangerous it always is to reason from insufficient data.” – The Adventure of the Speckled Band

“Data! Data! Data!” he cried impatiently. “I can’t make bricks without clay.” – The Adventure of the Speckled Band 

“I had,” he said, “come to an entirely erroneous conclusion which shows, my dear Watson, how dangerous it always is to reason from insufficient data.” – The Adventure of the Speckled Band

“I never guess. It is a shocking habit – destructive to the logical faculty.” – The Sign of Four

“Before we start to investigate, let us try to realize what we doknow, so as to make the most of it, and to separate the essential from the accidental.” – The Adventure of the Priory School

Focus on the details… 

“It is, of course, a trifle, but there is nothing so important as trifles.” – The Man with the Twisted Lip

“The little things are infinitely the most important.” – A Scandal in Bohemia

“It was most suggestive,” said Holmes. “It has long been an axiom of mine that the little things are infinitely the most important.” – A Case of Identity

“I am glad of all details,” remarked my friend, “whether they seem to you to be relevant or not.” – The Adventure of the Copper Beeches

“To a great mind, nothing is little.” – A Study in Scarlet

“You know my method. It is founded upon the observation of trifles.” – The Boscombe Valley Mystery

“Never trust to general impressions, my boy, but concentrate yourself upon details.” – A Case of Identity

“Elementary,” said he. “It is one of those instances where the reasoner can produce an effect which seems remarkable to his neighbour, because the latter has missed the one little point which is the basis of the deduction.” – The Crooked Man

“The world is full of obvious things which nobody by any chance ever observes.” – The Hound of the Baskervilles

“There is nothing like first-hand evidence.” – A Study in Scarlet 

“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

On the unusual vs. the commonplace… 

“Singularity is almost invariably a clue. The more featureless and commonplace a crime is, the more difficult it is to bring it home.” – The Boscombe Valley Mystery

“As a rule, the more bizarre a thing is the less mysterious it proves to be.” – The Red-headed League

“The more outré and grotesque an incident is the more carefully it deserves to be examined, and the very point which appears to complicate a case is, when duly considered and scientifically handled, the one which is most likely to elucidate it.” – The Hound of the Baskervilles

“Depend upon it, there is nothing so unnatural as the commonplace.” – A Case of Identity

“There is nothing so unnatural as the commonplace.” – A Scandal in Bohemia

Observe carefully… 

“You see, but you do not observe. The distinction is clear.” – A Scandal in Bohemia

“I see no more than you, but I have trained myself to notice what I see.” – The Adventure of the Blanched Soldier

“I can see nothing,” said Watson. “On the contrary, Watson, you can see everything. You fail, however, to reason from what you see. You are too timid in drawing your inferences.” –The Adventure of the Blue Carbuncle

Reason carefully… 

“When a fact appears to be opposed to a long train of deductions, it invariably proves to be capable of bearing some other interpretation.” – A Study in Scarlet

“Circumstantial evidence is a very tricky thing,” answered Holmes thoughtfully. “It may seem to point very straight to one thing, but if you shift your own point of view a little, you may find it pointing in an equally uncompromising manner to something entirely different.” – The Boscombe Valley Mystery

“One should always look for a possible alternative, and provide against it. It is the first rule of criminal investigation.” – The Adventure of Black Peter

“Holmes,” I cried, “this is impossible.” “Admirable!” he said. “A most illuminating remark. It is impossible as I state it, and therefore I must in some respect have stated it wrong. Yet you saw for yourself. Can you suggest any fallacy?” – The Adventure of the Priory School

Understand what is vital and what is incidental… 

“It is of the highest importance in the art of detection to be able to recognize, out of a number of facts, which are incidental and which vital. Otherwise, your energy and attention must be dissipated instead of being concentrated.” –The Reigate Puzzle 

“The principle difficulty in your case,” remarked Holmes in his didactic fashion, “lay in the fact of there being too much evidence. What was vital was overlaid and hidden by what was irrelevant. Of all the facts which were presented to us we had to pick just those which we deemed to be essential, and then piece them together in their order, so as to reconstruct this very remarkable chain of events.” – The Naval Treaty

“There is nothing more deceptive than an obvious fact.” – The Boscombe Valley Mystery

The power of deduction… 

“There should be no combination of events for which the wit of man cannot conceive an explanation.” – The Valley of Fear

“What one man can invent another can discover.” – The Adventure of the Dancing Men 

“You know my methods in such cases, Watson. I put myself in the man’s place, and, having first gauged his intelligence, I try to imagine how I should myself have proceeded under the same circumstances.” – The Musgrave Ritual

“Like all other arts, the Science of Deduction and Analysis is one which can only be acquired by long and patient study, nor is life long enough to allow any mortal to attain the highest possible perfection in it. Before turning to those moral and mental aspects of the matter which present the greatest difficulties, let the inquirer begin by mastering more elementary problems.” – A Study in Scarlet

“The detection of types is one of the most elementary branches of knowledge to the special expert in crime.” – The Hound of the Baskervilles

Some final thoughts… 

“My name is Sherlock Holmes. It is my business to know what other people don’t know.” – The Adventure of the Blue Carbuncle 

“We balance probabilities and choose the most likely. It is the scientific use of the imagination.” – The Hound of the Baskervilles

“Crime is common. Logic is rare. Therefore, it is upon logic rather than upon the crime that you should dwell.” – The Adventure of the Copper Beeches

“I never make exceptions. An exception disproves the rule.” –The Sign of Four

“Nothing clears up a case so much as stating it to another person.” – Silver Blaze

“Education never ends, Watson. It is a series of lessons with the greatest for the last.” – The Adventure of the Red Circle

“You know my methods. Apply them.” – The Sign of Four