[mjburgess]

> What else is an expression?

You seem to have confused expression with application. A person unable to speak but merely point is unable to express (that is, define precisely) what it is that causes them to point to, say: a red brick, a red door, a red pencil. However in their activity of pointing, that is, in their application of an unexpressed principle we can infer a "theory".

Naur's point is that a "theory" in his sense is a purely mental, immediate, intuitive ground for the understanding of a problem. It is the "red" in the above example, and as we cannot explicate red (only point to it) we cannot express the theory.

>If it matches something -- like software -- that is complex and determinate, it must itself be analysable into determinate properties or patterns or structure.

No. The mind is not a computer program. Mental models are not immediately accessible, completel and transparent to conscious thought, nor are their relations, nor are they "comprised" of anything simpler than more thoughts.

The theory doesnt "match" the computer program, the computer program is a symptom of the theory. The theory is how a problem is understood.

>Since 'theory' is used to make actual software -- something that can fit or diverge from it -- 'theory' must have a substantial, and complex, objective part.

I dont know what this means (nor much of your comment to be honest), but i suspect you're making the same error as above: that the (physical) products of mental activity reveal or constrain the nature and structure of that mental activity.

[hxa7241]

What is this 'theory' Naur talks of? It is not a nebulous feeling or sensation, it is something complex, articulate -- something 'built'. But how can something with logical structure be at the same time inexpressible? There is a contradiction lurking there.

Imagine you are 'building' one of these 'theories', to make some software. How do you know it is correct? The only way is by testing it against the world, and to do that it must be expressed. And any part that is not expressible cannot, for that reason, be a usable part of the 'theory'. (It is more basic really: a 'thing' in your mind, that cannot be expressed, is not really a 'thing' at all.)

The reason programmers are not simple replaceable resources is not because some kind of 'theory' thing is not expressible, but because making software requires certain significant practicalities of effort, knowledge, and skill.