"It can be maintained that Smith was a creator of general equilibrium theory, although the coherence and consistency of his work can be questioned. A fortiori, later systematic expositors of the classical system, such as Ricardo, J. S. Mill, and Marx, in whose work some of Smith’s logical gaps were filled, can all be regarded as early expositors of general equilibrium theory. Marx, in his scheme of simple reproduction, read in combination with his development of relative price theory in volumes 1 and 3 of Das Kapital, has indeed come in some ways closer in form to modern theory than any other classical economist, though of course everything is confused by his attempt to maintain simultaneously a pure labor theory of value and an equalization of rates of return on capital."