Thank you for your response. Perhaps I should try to give an example from my own field about what I’m trying to get at and what (I think) some of what John is proposing.
My main job nowadays is designing digital circuits. This involves thinking about the functionality the design needs to have and coming up with small pieces of logic that when connected together will provide that functionality. With modern formal languages, such as VHDL, the level of abstraction that I can use to describe these small pieces has increased immensely, as has the size of them.
For example, where as in the past I would have had to have drawn a schematic diagram showing the individual logic gates to implement a multiplier, today I can use the ‘*’ operator between two named signals and the software tools will infer a multiplier. So here is a first level of abstraction. When I’m designing circuits, I no longer think in terms of the logic gates in a multiplier, I think in terms of the type of multiplier I want. I know the connection is there to the gate, but it is of no real use to me.
Now, when I have finished the design, more often than not it will be required to control the implemented functionality with a microprocessor. I’ll choose the exact processor on the functionality it has. How that functionality has been achieved, I very rarely care. So now I’m thinking of complete systems and understanding the functionality that is useful to me. Could I look at the microprocessor schematic and see how it performs its wonders? Sure, but the complexity of it is likely to be too great for me to be able to understand the overall behavior.
So now we’ve got the block of logic that I designed and a block of logic I didn’t, but I’d argue that at an appropriate level of abstraction, I can understand both equally well for my needs.
The huge advantage to this approach is that I, a single person, can construct systems that are far beyond my ability to understand in their entirety. I think a similar approach could be useful in understanding how evolution of one level is related to evolution of another.