实证经济学方法论.pdf

Milton Friedman
Essays in Positive Economics
Part I - The Methodology of Positive Economics ∗
University of Chicago Press (1953), 1970, pp. 3-43

Introduction
In his admirable book on The Scope and Method of Political Economy John Neville
Keynes distinguishes among “a positive science … a body of systematized knowledge
concerning what is; a normative or regulative science…[,] a body of systematized knowledge
discussing criteria of what ought to be…[,]an art… [,] a system of rules for the attainment of
a given end”; comments that “confusion between them is common and has been the source of
many mischievous errors”; and urges the importance of “recognizing a distinct positive
science of political economy.”1
This paper is concerned primarily with certain methodological problems that arise in
constructing the “distinct positive science” Keynes called for - in particular, the problem how
to decide whether a suggested hypothesis or theory should be tentatively accepted as part of
the “body of systematized knowledge concerning what is.” But the confusion Keynes
laments is still so rife and so much of a hindrance to the recognition that economics can be,
and in part is, a positive science that it seems well to preface the main body of the paper with
a few remarks about the relation between positive and normative economics.
I. THE RELATION BETWEEN POSITIVE AND NORMATIVE
ECONOMICS
Confusion between positive and normative economics is to some extent inevitable.
The subject matter of economics is regarded by almost everyone as vitally important
to himself and within the range of his own experience and competence; it is the source of
continuous and extensive controversy and the occasion for frequent legislation.
Self-proclaimed “experts” speak with many voices and can hardly all be regarded as