What is a newspaper?
Levels of Abstraction
. . . . something as simple as a newspaper might be specified to six levels, as in Douglas Hofstadter's illustration of that ambiguity, with a progression from abstract to concrete in Godel, Escher, Bach (1979):
(1) a publication]
(2) a newspaper]
(3) The San Francisco Chronicle]
(4) the May 18 edition of The San Francisco Chronicle]
(5) my copy of the May 18 edition of The San Francisco Chronicle]
(6) my copy of the May 18 edition of The San Francisco Chronicle as it was when I first picked it up (as contrasted with my copy as it was a few days later: in my fireplace, burning)]
An abstraction can thus encapsulate each of these levels of detail with no loss of generality. But perhaps a detective or philosopher/scientist/engineer might seek to learn about something, at progressively deeper levels of detail, to solve a crime or a puzzle. (from wikipedia @ https://en.wikipedia.org/wiki/Abstraction)
Thus we can understand the word newspaper on many logical levels. That is; the many levels all taken together are an abstraction. All of these levels can be the case at same time. A person is aware of the context that the word is being used in and plucks the right meaning out of the abstraction.
There is also a contrast involved between something abstract and something concrete. Abstractions are similar to platonic forms. The word apple stands for an abstraction and an apple in my hand is a concrete example. Numbers present another sort of example that in an interesting way depends on abstractions that can have concrete examples. Just saying "2" doesn't say much. But saying "here are 2 apples" says quite a bit.
I've combined these two ideas of "logical level" and abstraction into the idea of "levels of abstraction". I think I got the idea 40 years ago from Gregory Bateson's book Steps to an Ecology of Mind but I don't have a copy of it now and I admit that I can't find any reference to it. But the idea is attractive enough to me that I claim it as my own too. I'm motivated by a philosophic need to ground things like cognition (as an extreme example) in physical reality.
The common view of atomic physics demonstrates the idea pretty clearly. We have protons and neutrons and electrons that have certain properties. Those properties let them combine to make atoms. That's going up one level. You can see how the subatomic particles are made of things like quarks. That's going down one level. I've found that you can go up through many levels. Atoms make molecules with properties that atoms don't have - chemistry. Biology is a level where things are made of molecules but can do other things like crawl around And the capacity to crawl around enables cognition.
I call those levels "levels of abstraction" One friend told me that the label gives her hives. But - hey - I do need a label for the idea and this is the one that I think fits. I'm not strongly attached to labels and if there is a better one then I'd like to see it.
I think the motivation to use "levels" is obvious from what I've said already but I do acknowledge the problems with using a spatial reference - levels are not really above or below and certainly no level is the 'real' level.
The motivation for "abstraction" is a bit more subtle.
It's like all of the levels in the newspaper example are true at once - forming an abstraction that has properties that the levels themselves don't have. (note these are logical levels)
That is: you can read a newspaper - all those things that are not readable create something that is readable.
When properties of lower level things combine to produce higher level things - I call that abstraction.
et voila!! Levels of Abstraction!