What your fingers know, but your intellect can't fully explain.
(i.e. the skill is partly unconscious rather than fully articulated)The thesis of personal knowledge was developed by Michael Polyani in his book "Personal Knowledge: Towards a Post-Critical Philosophy (1958).
It has the subtitle: "A chemist and philosopher attempts to bridge the gap between facxt and value, science and humanity"
His focus is on acts of skill that are unique and personal, but result in objective knowledge. Such is the skill of a microscopist of Barbara McKlintock's calibre, that she saw things in cells that were only confirmed many years later by molecular biologists. Such is the skill of a geneticist such as Seymour Benzer to design elaborate sets of individually intricate experiments that hang together into a body of theory. Einstein imagined himself as racing a light beam, and wondered what happens the moment he catches up. Kekule (I think that was the name) dreamed the structure of Benzene.
In all of these cases, the knowedge obtained is independantly verifiable and "objective". However the act of gaining that knowledge begins in an individual physiology, a unique psychology, personal circumstane and imagination that is wholly subjective.
I had the opportunity to work with good electron microscopists and realize that I would never be excellent (and struggled to be merely adequate) at sample preparation, simply due to a level of poor-hand-eye coordination, regardless of what level of theoretical knowledge I obtained. However, I compensate by being very near sighted, and able to see things with my glasses removed that other people seem to only be able to see under a dissecting microscope. That makes me fairly competant at areas like seed biology, where a lot of diagnostics can take place at the level of surface morphology and a few cutting tests.
Any act of skill, when practiced repeatedly goes "subconscious". So a skilled martial artist, simply moves as the target moves. She doesn't stand there and evaluate; run through a list of "lawful defensive moves". She simply moves as her body has been trained to. But, by going subconscious, by moving from thought to intuition, it becomes hard to talk about the skill itself. It has become innate, and beyond verbalization. Such skills have to be learned by each person anew, in their own way. These aren't skills from the text-books. They are skills from within the psyche, written upon the body.
So there is a bit of mystery here. Science is about method -- in Popperian views -- almost wholly about the method of falsifying a discovery once made. However, it is the process of discovery, as Feyerbend has emphasized, where the real excitement is. "Anything Goes". Personal mythologies come into play. Quirks of physiology come into play. Prejudices come into play.
The justly reviled Eugenics movement was the active motiviation for much of Fisher's genetic research. Wright fundamentally objected to the movement on moral grounds, and yet was capable of doing equally good research. Fisher's methods stressed calculation. Wright's methods stressed semi-graphical techniques, culminating in path analysis (and the FisherWright formalistvisualizing-tinkerer duality echoes in the Schwinger/Feynman tension over the validity of Feynman diagrams relative to more formal techniques)
The scientific method is post the creative act. It is a rule of judgement (does this creative act lead to objective knowledge?). The creative act is where that spooky action at a distance resides. Creative acts of skill seem more in the realm of art. And the viewpoint of Personal Knowledge essentially supposes (though I don't believe Polyani stated it that way) that the Art is the mother of the Science.
Now, could any of this apply to the observation that there is a difference in qualitative rather than merely quantitative scale between adequate and excellent programmers. Take two programmer's, one adequate, one excellent (by whatever objective standard of excellence you and two other's can agree to). Is it likely that schooling made the difference? Mentoring? Coaching? Application of XP, Scrum, Methodology-du-jour???
Personal Knowledge?
I was lucky enough to work for several years with a programmer who is better on his bad days than I am ever likely to be on my good days. One thing that I found really interesting in working side-by-side with him over a number of years, was that he reacted almost physically to what he considered bad, non-elegant, poorly formatted code. He was really odd in that he could program continuously for several hours, and the code would run the first time. The programmers who worked with him tried to emulate him (he was our de-facto living coding standard) and he was the go-to guy when a program just wasn't working, and the bugs weren't being found. I learnt a tremendous amount from him. I try and copy the clarity of his code every day when I write my own. But I'll never be able to code as fast and with as much quality 1st time quality as he can (I have to go slower, and iterate to keep the quality up).
My process of getting to "it runs" is more humble and mundane. I make mistakes. I have to slow down and think things through. I have to draw lots of pictures to work out connections between things rather than holding all the connections in my head. I'm continuously running and debugging fragments of code, rather than write continuous short-stories and novella's of code. He can get away without unit testing. I can't.
So, whatever he does, whatever makes him an objectively excellent programmer (as measured by his ability to produce rapidly code that works today and is still readable a year later), I can't emulate it. Instead, I have to find my own path towards personal knowledge. In my case -- I worked with metrical poetry forms for several years, and have a good "ear" for rhythm. So I try and train my code ears. That sounds odd -- and it's hard to verbalize what I mean. The best way I can put it is, I try to get to the same level of hearing "alternate meanings in a phrase" with code, as I used to with poetry. But that's just my way, and your way, your path to personal knowledge might be similar, or so different this last paragraph makes no sense.
You either grok someone else's personal knowledge via a shared intuition -- or not at all.