David D. Friedman: Economics

“[T]he assumption describes our actions, not our thoughts. If you had to understand something intellectually in order to do it, none of us would be able to walk.
Economics is based on the assumption that people have reasonably simple objectives and choose means to achieve them. Both assumptions are false-but useful.
Suppose someone is rational only half the time. Since there is generally one right way of doing things and many wrong ways, the rational behavior can be predicted but the irrational cannot. If we assume he is rational, we predict his behavior correctly about half of the tie - far from perfect, but a lot better then nothing. If I could do well at the racetrack I would be a very rich man.
[R]ationality is an assumption I make about other people. I know myself.
[R]ationality is an assumption I make about other people. I know myself well enough to allow for the consequences of my own irrationality. But for the vast mass of my fellow humans, about whom I know very little, rationality is the best predictive assumption available.”

David D. Friedman

As cited in Ronald J. Baker (2010) Implementing Value Pricing: A Revolutionary Business Model for Professional Firms. p. 122
Source: Hidden Order: The Economics of Everyday Life, 1996, pp.3-5

“David D. Friedman is the one of the most important living anarcho-capitalist philosophers. He has added a philosopher's insistence on consistency to the firm grasp of economic principles he presumably learned at the paternal knees.”

David D. Friedman

In The Pragmatist. (1998), Vol.14, p. 77
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“Economics is that way of understanding behavior that starts from the assumption that people have objectives and tend to choose the correct way to achieve them.”

David D. Friedman

Price Theory: An Intermediate Text, 1986