This is Chapter 5 from my book: Ellerman, David. 1995. Intellectual Trespassing as a Way of Life: Essays in Philosophy, Economics, and Mathematics. Lanham MD: Rowman & Littlefield.
When an orthodox economist considers the principle of people getting the fruits of labor, he or she will invariably interpret it in terms of marginal productivity. The orthodox claim is that under the conditions of competitive equilibrium, each unit of labor “gets what it produces.” Well-meaning capitalist liberals emphasize that actual capitalism may be neither competitive nor in equilibrium, and in any case, there are enormous difficulties in measuring the “marginal product of each factor of production.” In other words, they accept that interpretation of marginal productivity theory in principle but fuss about its applicability in practice.
