6. Normative or Descriptive Theory. The purpose
of a theory of decision-making, or specifically of game
theory, is to advise a person how to behave by choosing
optimally from the set of his available strategies, in
situations subject to the theory. If he decides knowingly
to deviate from the indicated course he has either
substituted another goal, or dislikes the means (for
moral and other reasons). It is then a matter of termi-
nology whether he is still considered to be a rational
actor. The theory at any rate can take such deviations
into consideration. Clearly, some technically available
strategies may be inadmissible in legal, moral, and
other respects. In some cases these questions do not
arise: chess is played equally whether the opponents
are rich, poor, Catholics, Muhammadans, communists
or capitalists. But business or political deals are affected
by such circumstances. Advice can be given with or
without constraints which involve morals or religion.
The theory is also descriptive, as it must be if it is
to be used as a model. It might be argued that the
theory cannot describe past events since before it was
created individuals could not have followed the
optimal strategy which only the theory could discover!
The answer is that for some situations the individual
can find it by trial and error and a tradition of empirical
knowledge could develop after repeated trials. How-
ever, the same objection applies regarding ordinary
maximum problems (provided they are even given):
the identification and computation of the maximum
was (and in many cases still is) out of reach even for
very large organizations; yet they behave as if they
could find it and they try to work in that direction.
Theories thus can be viewed as being both descrip-
tive and normative. In the natural sciences a similar
apparent conflict shows up in interpreting phenomena
as either causally or teleologically related, while in fact
this distinction may resolve into merely a matter of
how the differential equations are written.
Thus the theory is capable of being used in both
manners. Future descriptions of reality will be im-
proved if the concepts of the theory are available and
future actions of those who use the theory in order
to improve their own rationality will be superior (ex-
cept in the simplest cases where the correct answer
is also intuitively accessible). Clearly, if more and more
players act rationally, using the theory, there will be
shifts in actual behavior and in real events to be de-
scribed. This is an interesting phenomenon worth
pointing out. It has philosophical significance: progress
in the natural sciences does not affect natural phenom-
ena, but the spread of knowledge of the workable social
sciences changes social phenomena via changed indi
vidual behavior from which fact there may be a feed-
back into the social sciences (Morgenstern, 1935).
