In short, this is an observation that the average number of related “data chunks” a person can recall is seven, plus or minus two.
This is usually specified as for short term memory, but may be relevant to longer term memorization of lists too.
A friend of mine is working on a language-related project. It seemed to me that if you must have lists of categories or affixes, then breaking them up into groupings of seven or less might be a good approach.
I know six is not seven, but bear with me a moment.
I remember this list by recalling that three things on it are “flexible”: hat, rope, “towel”; and that three are not: medicine, writing kit and fire tube.
As I point out in my earlier article, this list does not include a knife, since telling a ninja or any other sensible person of that era to carry one was probably redundant. If we add knife/tool to the list it becomes seven.
OK, I thought, does what I have on me right now meet the criteria of the six/seven tools of travelling/everyday carry (EDC)?
Firstly, I have a hat. It’s cold out and my head has little remaining natural insulation. If it was sunny out and I was planning to spend any time outside I would probably have a hat of a different design.
Rope, or cordage at least. I have a spare shoelace tucked into the bottom of a pocket. I also have the dental floss in my pocket kit which can be used for a variety of purposes.
“Towel”. The item the ninja regarded as a towel was a relatively thin, multipurpose item. I have a bandanna in my pocket which can serve similar purposes, including as an emergency hat.
Medicine. My pocket kit contains plasters, painkillers and disinfectant wipes.
Writing kit. I have a pencil. I can also write things down on my phone.
Fire. No ninja tube of smouldering charcloth, but I do carry a source of fire. A lighter rides in the same pocket as the bandana and shoelace.
Knife. I carry a Swiss Army knife and a mini-Leatherman squirt and have a Swiss Army classic mini-knife on my key ring.
These seven tools do not just represent concrete objects.
They also represent broader, more generic categories.
For example, the hat also represents shelter, so includes a coat suited to the weather, scarf and gloves should they be needed and the survival blanket I carry.
The writing kit also represents communication, so includes my phone and the USB drive I carry. Communication can include signalling, which includes my phone and the whistle and photon light on my keychain. Illumination can be taken as a subset of signalling.
The knife also represents tools in the narrower sense, so includes my mini-prybar, diamond sharpening card and the P38-style can opener on the keychain. The knife also represents the requirement for self-defence, where such is permitted.
As can be seen, the “seven tools of EDC” are a good starting point for planning an EDC or larger kit.
There are other categories, of course.
Money is always useful and documentation may be needed.
I carry tape, pins and other items that might be used for repairs. These might be considered a subset of the knife/tools category. I may add a magnetized needle and a few feet of invisible thread to my little bag of pins and paperclips.
None of the seven categories really covers navigation, but I do carry a Suunto clipper compass which has proved to be surprisingly useful in town.
On the next level up, food and water, or the means to procure and prepare them should be addressed. At the EDC level this is addressed by the money and credit card.
If you live in a very hot, dry environment carrying a supply of water on your person is prudent.