This book provides the missing theoretical link between Sraffa's Production of Commodities by Means of Commodities and Debreu's Theory of Value. Its thesis is that both classical and neoclassical value theory operate through arbitrage and speculation in the financial markets. Key among those markets is the bourse or stock market. Once a stock market is incorporated into general-equilibrium theory, the classical analysis of value (a la Ricardo, Marx and Sraffa) and the neoclassical theory of price (descending from Walras, Hicks and Arrow-Debreu) can be seen to possess the same mathematical structure. Thus the modern theory of arbitrage pricing in financial markets is capable of bringing together the two great rival schools of economic thought.