Visualizing the Building Theory using BBC Sherlock
@amateur-deductions recently did a post on the Building Theory. In his words:
[The Building Theory] serves as a wonderful way to illustrate how much a deduction is a progressive process, with multiple little steps between observations and conclusions. It's also an amazing tool to analyze other people's deductions and break them down in a way that allows you to map out their trains of thought and learn from them
He provides an excellent explanation of how the theory works: basically, you think of the process of deducing as constructing a building, with observations and subsequent deductions representing bricks that are stacked on top of one another, building up to more complex deductions based on those original observations & deductions.
I’ve always liked this theory because it makes the process of deduction more tangible and visual, which helps me learn, and I know others like to use visuals to learn too.
I’ve mapped out deductions from BBC Sherlock before, so I thought sharing that here would help provide a visual supplement to @amateur-deductions‘ work.
When Sherlock and John first meet, Sherlock asks: “Afghanistan or Iraq?”
You can watch the scene where he asks that here. And the scene where he explains how he got to that here.
While the show provides a decent verbal breakdown of how Sherlock got to that question, we can also visualize his process like this:
blue: observations // green: deductions made from observations // pink: deductions made from prior deductions & observations (level 1) // yellow: deductions made from prior deductions (level 2)
As you can see, Sherlock uses his initial observations about John to make deductions, and then uses those deductions to make additional deductions. All of this culminates in him asking John “Afghanistan or Iraq?”
Let’s break down this process a bit. We can think of this building as being made up of a bottom floor, and then two supporting sides that work together to build onto that bottom floor and also support the roof placed on top.
First, the bottom floor:
When John enters the room, Sherlock looks up at him and makes four observations about him, which he uses to make two deductions.
1. stance + haircut = military
** Sherlock knows that these observations = military from knowledge he has about the appearance/behavior of people in the military.
2. looks around the room + says “bit different from my day” = medically trained at Bart’s Hospital
** Here Sherlock uses a combination of knowledge and logic. He knows that Bart’s Hospital is a well-known training hospital and if John is familiar with the lab that the pair are standing in (as opposed to a patient room), he must have been a student there.
Sherlock then takes those two deductions and combines them to create another: military + medically trained = army doctor. That deduction forms the base of the rest of the building.
Next, there are two supporting sides. Let’s call them the “limp” side and “tan” side, as those are the two observations that form the base of each.
First, the limp:
Sherlock begins with several observations:
1. has a limp and uses a cane.
2. does not ask for a chair to sit in.
** Knowledge: Sherlock knows that people with limps may look for or ask for somewhere to sit.
From this, Sherlock deduces that John:
1. forgets he has the limp.
2. Why? Because the limp is psychosomatic.
** Knowledge: Sherlock knows about psychosomatic injuries.
3. Which means that trauma caused the limp.
Second, the tan:
Again, Sherlock begins with two observations, and each have their own subsequent deduction.
1. has a tan. = was recently in a sunny place.
** Knowledge: Sherlock knows that people get a tan from being in the sun, and that tans fade over time.
2. only has a tan on his hands and face. = was in a sunny place while wearing long sleeves, so he was not on vacation or sunbathing, but was on business.
** Knowledge: Sherlock knows that when people go on vacation to a sunny location, it is not typical to wear long sleeves or professional clothing but rather dress casual (shorts and a t-shirt, swimsuits, etc.).
Here is where Sherlock’s process culminates into the question. Relying on the deduction that John is an army doctor, and combining that deduction with these two new deductions (1) has a limp from trauma, and (2) was recently in a sunny place for business/work, Sherlock makes this final deduction: John is an army doctor who was recently in a war zone near the tropics.
He cannot go further than this though, as there are a few locations that fit that description. So, Sherlock engages in order to get the information he needs: “Afghanistan or Iraq?”
~
I hope this provided a helpful visual example of the Building Theory - if anybody has any questions or wants me to go into more detail on any aspect of this example, please ask!