(publ. University of Chicago Press)
Milton Friedman's book Essays in Positive Economics (1953) is a collection of earlier articles by the author with as its lead an original essay "The Methodology of Positive Economics." This essay posits Friedman's famous, but controversial,[citation needed] principle (called the F-Twist by Samuelson) that assumptions need not be "realistic" to serve as scientific hypotheses; they merely need to make significant predictions.