During the case of the Speckled Band, Sherlock Holmes had to unravel Julia Stoner's mysterious death, two years previously. Decisive action was imperative to prevent an identical fate befalling the victim's sister at the hands of their vicious stepfather.
Holmes's purpose - to find out what is going to happen to Helen Stoner and stop it in time - determines his examination of her room, the scene of the impending crime.
Holmes never theorises without facts, basing his conclusions on what he finds and what he already knows. To discover if an assailant could enter the room he tries the window shutters and searches the floor and ceiling for trap doors. He merely casts an eye over the bedroom door, confirming Helen's prior testimony that it is indeed secure, once locked from the inside, as it was on the night of her sister's death.
A bed which is permanently fixed to the floor, directly below a comparatively new-looking bell-pull rope which does not work, and a ventilation shaft leading to the next room instead of outside, arouse Holmes's suspicions. From here, he needs further information to substantiate his theory and finds out from Helen that these items were installed just before her sister's death.
Holmes already knows that the sisters' stepfather is a doctor of medicine, that he brought a number of animals back to the house from a trip to India, and that Julia had died suddenly in dim light, without a mark on her body, uttering the words: "It was the speckled band." He then sets out to find the final pieces of the jigsaw. Where will he go next, why, and what he will be looking for?
The connection between observation and deduction has applications across the curriculum. When observing, we decide what is relevant or irrelevant, important or unimportant, by reference to the purpose of our enquiry.
Subsequently, as we draw conclusions from our observations, we must refer to the facts if we are to avoid ambiguities, inaccuracies or mistakes. In other words, children can follow in the footsteps of Sir Arthur Conan Doyle's great Victorian detective.
Observing characters acting, speaking and, especially, interacting, can give insights into their nature and how they might behave in different circumstances. But can we be sure that a person who reacted angrily in one situation would necessarily do so in another? What further observations would we need to make before we could substantiate this assumption?
Similarly, in a numeracy session on the interpretation of data, some conclusions - for instance, "more children travelled to school by foot than by bike" - would be apparent through observation alone. Others, such as "What is the preferred method of transport to school?" would still be ambiguous if one used numbers from a data chart alone. What subsequent enquiries would need to be made in order to put forward an accurate answer to that question?
When seeking to discover whether the lives of poor children changed for the better during Victorian times, a number of sources might be used. Keeping their purpose in mind, pupils will need to scan the information, selecting what is relevant, discarding what is less so, before combining their findings with any prior knowledge. Only then can they form a valid opinion.
Similar methodology can be used when looking at contemporary issues. Do we need a new main road? Should the swimming pool be closed? People will have contradictory opinions based on beliefs and experiences.
For instance, a home-owner living near the proposed road might not be so objective as someone living on the other side of town.
In every case, knowledge is the essential precursor of deduction.
Throughout his career, Holmes left no stone unturned in accruing a vast amount of knowledge to assist him with his enquiries, enabling him to understand better, and to organise the specifics of each case. His thoroughness is perhaps Holmes's final lesson to all who wish to be accurate in their assumptions and successful in their lives.