David Director Friedman is an economist, physicist, legal scholar, and libertarian theorist. He is known for his writings in market anarchist theory, which is the subject of his most popular book, The Machinery of Freedom (1973). He has authored several other books and articles, including Price Theory: An Intermediate Text (1986), Law's Order: What Economics Has to Do with Law and Why It Matters (2000), Hidden Order: The Economics of Everyday Life (1996), and Future Imperfect (2008).