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社會科學概論
高永光老師
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The
Methodology
of Modelling
 The
term 'model' is, however,
rather vague. It is used in a
variety of different ways by social
scientists and, in addition, it is a
common-speech term with a
variety of different meanings.
A. EXAMPLES OF MODELS
 1.
The circular flow of
expenditure
 This is the model of the economy
as a circular flow of expenditure,
which is the foundation of the
branch of economics called
'macroeconomics'.
 The
theories of modern
macroeconomics are too complex
to be stated without using
mathematics, but their central
concept of a circular flow of
expenditure can be modelled in a
simple diagram: Figure 6-1.
 In
this diagram the economy is
depicted as a flow of
expenditures between two
entities called 'individuals' and
'firms'. All production is presumed
to take place inside firms.
 The
firms buy 'factors of
production' ( labour, the use of
capital equipment, raw materials)
in order to carry on their
production processes and the
expenditures
 they
make for these factors are
received by individuals who (as
workers and property owners)
are pictured as selling these
services to firms.
 Individuals,
in turn, make
expenditures, buying finished
commodities from firms.
 2.
The market model
 The study of how this is
accomplished by ‘markets’ is
the main focus of the branch
of economics called
'microeconomic theory’.
 Its
principal objective is to
analyse how market processes
determine the quantities of
specific goods that will be
produced (and used) and the
prices at which they will be
sold.
 The
basic idea of microeconomic
theory is that markets are twosided: the purchasers (or users)
of commodities on one side of
the counter, so to speak, and the
producers (or sellers) on the
other.
 What
ensues - the quantities
of goods produced and used,
and their prices - is the result
of the interaction of ‘the
forces of supply and demand’.
 In
a general way this conception
of market processes goes back to
the eighteenth century and
earlier; but if doing little more
than stating the obvious to say
that price is ‘determined’ by
‘supply and demand’.
 3.
The prisoners' dilemma
model
 For a third illustration of model
construction let us look at one
that focuses , on the important
fact that when a person engages
in an action the outcome may
depend in part on what other
people do.
 This
is obviously the case
when one is engaged in a
game like, say, bridge or
chess, which has to be played
with a strategy that takes into
account the potential actions
of the other players.
 Realization
that many social
situations are similar has led to
the construction of social models
built upon the theory of games.
 John
von Neumann and Oskar
Morgensten, The Theory of
Games and Economic
Behaviour (1944), was the
pathbreaking work in this.
(Note again how recent this
is.)
 The
particular game model
known as the 'prisoners'
dilemma' has been widely
used in virtually all the
disciplines of social science.
B. SOME FEATURES OF
MODELS
 In one respect, however, they
may present a misleading
picture of contemporary social
science research, since they
were discussed purely as
theoretical models.
 If
one looks at the current
literature of the social sciences it
is immediately evident that most
research is quantitative and
empirical, making use of data
from surveys reports, censuses,
etc.,
 and
processing such data by
complex statistical methods that
have been developed (by
physicists, biologists, and
mathematicians as well as social
scientists), especially during the
past half-century or so.
 It
is not true that if something
cannot be measured it is not
worth talking about but, none the
less, it is true that when we can
measure we can talk more
precisely.
 In
some of the general
discussion of models by
philosophers of science much
emphasis is placed upon a
quality called 'isomorphism‘.
 This
term is extensively used
in biology and the other
natural sciences, as well as
mathematics, to refer to a
structural correspondence
between two or more things .
a model is described as
'isomorphic' what is usually
meant is that there is a high
degree of correspondence
between the model and the
‘real thing’.
 When
 If
isomorphism were a necessary
characteristic of models the social
sciences would not do much
modelling, because constructing
a model that corresponds to a
real society in any direct way is
not possible.
 From
what has already been said
about isomorphism it is evident
that models are simpler than the
real-world things or processes
they represent. If this were not
so, models would be as complex
as the real-world phenomena
themselves, and just as
incomprehensible.
 The
whole point in building an
analytical model is to
construct a representation
that is simpler than the real
thing.
 It
is not a valid criticism of a
model to say that it is
necessarily wrong because it
is simpler than the reality it
purports to represent.