Book Ch: The Methodology of Positive Economics, Friedman (1953)

Chapter 1 in Friedman's Essays in Positive Economics (1953). Reprinted in several editions of The Philosophy of Economics: an Anthology, by Hausman (2007, 2012).
== Summary ==
=== Intro ===
Keynes in The Scope and Method of Political Economy distinguishes between:
# Positive science: a body of systematized knowledge concerning what is.
# 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.
This essay is concerned with methodological problems that arise in constructing the "distinct positive science" that Keynes called for. In particular, with the problem of how to decide whether a suggested hypothesis or theory should be tentatively accepted as part of the "body of systematized knowledge concerning what is". 
=== I. The Relation between Positive and Normative Economics ===
Keynes lamented the confusion between the above three categories, and because Friedman notes this is still common, he starts with a brief remark on this distinction. 
=== II. Positive Economics ===
=== III. Can a Hypothesis be Tested by the Realism of its Assumptions? ===
=== IV. The Significance and Role of the "Assumptions" of a Theory ===
=== V. Some Implications for Economic Issues ===
=== IV. Conclusion ===