Reaching Conclusions

‘It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth.’
‘THE ADVENTURE OF THE BERYL CORONET’
Holmes’s gift (and occasional curse) was his unearthly ability to alight upon the truth where others had failed to do so.



To conclude your crash
course in thinking like the Great Detective, let’s take a look at the modus operandi he used to reach the right answer so often:
Be in the right frame of mind
Seeking the truth is an exercise best done when rested and relaxed. Fuel yourself too. A team of researchers in 2010 found that making
judgements is best achieved when your blood sugar levels are at their optimum level.
Gather your raw information
As we have seen, Holmes gathered data from a huge range of sources – the crime scene, eye-witnesses, personal experience, reference
materials etc.
Evaluate the data
Set aside that which seems flawed or not useful.
Be a reader of human nature
In The Sign of Four, Holmes quoted the historian and philosopher, Winwood Reade, on the subject:
He remarks that, while the individual man is an insoluble puzzle, in the aggregate he becomes a mathematical certainty. You can, for example,
never foretell what any one man will do, but you can say with precision what an average number will be up to. Individuals vary, but percentages
remain constant. So says the statistician.
Search for the anomaly
The out-of-place detail can be the thread that unravels an enigma. As Holmes said, ‘what is out of the common is usually a guide rather than a
hindrance.’
Think the unthinkable
As Holmes proclaimed in The Valley of Fear, ‘how often is imagination the mother of truth?’
Formulate your hypotheses
Evaluate the likelihood of each hypothesis against the known facts. When Holmes was accused of straying into guesswork in The Hound of
the Baskervilles, he responded: ‘Say, rather, into the region where we balance probabilities and choose the most likely. It is the scientific use
of the imagination, but we have always some material basis on which to start our speculation.’
Don’t mistake correlation for causation
As an example, we live in an age when the ice caps are melting and obesity is increasing, but that does not mean one causes the other or that
they are linked in any way beyond coincidence.
Be rigorous
Do not become fixated on a single particular theory. Entertain all the possibilities.
Exclude the impossible …
Perhaps Holmes’s guiding maxim – a hypothesis that does not fit the facts must be dismissed. Eventually you will be left with the only theory
which complies with all the facts. No matter how unlikely it seems, this must be the truth.
Now, to paraphrase the Great Detective, you now know his methods. Use them!