There are two aspects of the concept of abstraction, as it is used:
in the context of the modelling scheme *, and in the context
of metasystem transition in the language.
The vertical lines on the scheme of modelling are functions, or mappings,
from the states of the world W to representations R (the states of the
language L of the model). This mapping is always
an abstraction: some aspects of the state of the world are necessarily
ignored, abstracted from, in the jump from reality to its description.
The role of abstraction is very important: it reduces the amount of
information the system S has to process before decision taking.
The simplest case of abstraction, mathematically,
is when the states of the world wi
are described by a set of variables w1,w2,...,wn, and we can separate
those variables, say w1,W2,...,wm, on which M really depends,
from the remaining variables wm+1,...,wn,
on which it does not really depend, so that
M(w1,w2,...,wm,x{m+1},...,wn) = M'(w1,w2,...,wm)
We often use the same word to denote both a process and its result.
Thus all representations ri resulting from mapping will be also referred
to as abstractions. It should be kept in mind, however, that abstraction
is not so much a specific representation (a linguistc object),
as the procedure M which defines what is ignored and what is
not ignored in the mapping.
Obviously, the object chosen to carry the result of abstraction
is more or less arbitrary; the essense of the concept is in the
transformation of wi into ri.
Mathematically, an abstraction ri can be defined as the set of all
those states of the world w which are mapped on ri. i.e. the
set of all w such that M(w) = ri. The abstraction 'tea-pot' is the set
of all those states s in S which are classified as producing
the image of a tea-pot on the retina of my eyes.
A cybernetic system, depending on its current purposes, may be
interested in different parts, or aspects of reality. Breaking the single
all-inclusive state of the world wi into parts and aspects is one of the
jobs done by abstraction. Suppose I see a tea-pot on the table,
and I want to grasp it. I can do this because I have in my head
a model which allows me to control the movement of
my hand as I reach the tea-pot. In this model, only the position and
form of the tea-pot is taken into account, but not, say the form of
the table, or the presence of other things on it. In another
move I may wish to take a sugar-bowl. And there may be a situation where
I am aware that there are exactly two things on the table: a tea-pot and
a sugar-bowl. But this awareness is a result of my having two distinct
abstractions: an isolated tea-pot and an isolated sugar-bowl.
The other aspect of abstraction results from the hierarchical nature of
our language.
We loosely call the lower-level concepts of the linguistic
pyramid concrete, and the higher-level abstract. This is a very
imprecise terminology because abstraction alone is not sufficient
to create high level concepts. Pure abstraction from specific
qualities and properties of things leads ultimately to the lost
of contents, to such concepts as `something'. Abstractness of a
concept in the language is actually its `constructness', the
height of its position in the hierarchy, the degree to which it
needs intermediate linguistic objects to have meaning and be
used. Thus in algebra, when we say that x is a variable, we
abstract ourselves from its value, but the possible values
themselves are numbers, which are not `physical' objects
but linguistic objects formed by abstraction present
in the process of counting. This intermediate linguistic level of
numbers must become reality before we use abstraction on the next
level. Without it, i.e. by a direct abstraction from countable
things, the concept of a variable could not come into being.
In the next metasystem transition we deal with abstract algebras,
like group theory, where abstraction is done over various operations.
As before, it could not appear without the preceding
metasystem level, which is now the school algebra.