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.
Through the ages, the professional users of tools by and large have not needed to, been able to, or wanted to talk to outsiders about their implements. They did not need to because tools themselves are used to make other tools, and thus users could very often fashion a new tool with their old ones. If they did need to communicate the design for a new tool to someone outside their trade, they could do so without having to reveal the tool's intended use...Besides, the inventive process of conceiving a new tool was often a nonverbal one. Finally, craftsmen were unwilling to share information about their specialized tools because to do so would have been to give up their competitive edge and their value to those outside the craft.