The primary thing when you take a sword in your hands is your intention to cut the enemy, whatever the means. Whenever you parry, hit, spring, strike or touch the enemy’s cutting sword, you must cut the enemy in the same movement. It is essential to attain this. If you think only of hitting, springing, striking or touching the enemy, you will not be able actually to cut him.
The McNamara fallacy, named for Robert McNamara, the US Secretary of Defense from 1961 to 1968, involves making a decision based solely on quantitative observations (or metrics) and ignoring all others. The reason given is often that these other observations cannot be proven.
The fallacy refers to McNamara's belief as to what led the United States to defeat in the Vietnam War—specifically, his quantification of success in the war (e.g., in terms of enemy body count), ignoring other variables.
A Fermi estimate is a quick-and-dirty solution to an arbitrary scientific or engineering analysis problem. Fermi estimation uses widely known numbers, readily observable phenomenology, basic physics equations, and a bunch of approximation techniques to arrive at rough answers that tend to be correct within an order of magnitude or so. The term is named for Enrico Fermi, who was famously good at this sort of thing.
…It struck me that there is counterpart to this kind of thinking on the synthesis side, where you use similar techniques to arrive at a very rough design for a complex engineered artifact. I call such a design approach Dyson design, after the physicist Freeman Dyson, who was one of the best practitioners of it (not to be confused with inventor James Dyson, whose designs, ironically, are not Dyson designs).