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.
Learning to design is, first of all, learning to see. Designers see more, and more precisely. This is a blessing and a curse—once we have learned to see design, both good and bad, we cannot un-see. The downside is that the more you learn to see, the more you lose your “common” eye, the eye you design for. This can be frustrating for us designers when we work for a customer with a bad eye and strong opinions. But this is no justification for designer arrogance or eye-rolling. Part of our job is to make the invisible visible, to clearly express what we see, feel and do. You can’t expect to sell what you can’t explain.
This is why excellent designers do not just develop a sharper eye. They try to keep their ability to see things as a customer would. You need a design eye to design, and a non-designer eye to feel what you designed.