"There are two things in Sraffa. One of them is very close to Keynes and that's the part that the Sraffians ignore and that is, Sraffa wrote a criticism of Hayek's capital theory book in 1932, and it's in that criticism that Sraffa developed this theory of spot and forward markets, and it's that theory which Keynes latched onto in his spot-forward market analysis. So there's a very good connection between Sraffa and the spot-forward markets. The other thing which they've latched onto, what was really anti-Keynesian, is The Production of Commodities by Means of Commodities. It has nothing to do with real world or with economics - it's an attack to show that the neoclassical system doesn't work. There are lots of ways of showing that it doesn't work, but basically the way Sraffa shows it doesn't work is by assuming that there's no substitutability between labour and capital. It's a fixed-coefficient system. So what? You know, the old neoclassicists would have said that wages were inflexible. It's the same thing. Real wages are inflexible in the Sraffian system. What does it prove? I don't think it proves anything."