Book excerpt: Mr Dobb examines the history of economic thought in the light of the modern controversy over capital theory and, more particularly, the appearance of Sraffa's book The Production of Commodities by Means of Commodities, which was a watershed in the critical discussions constituted a crucial turning-point in the history of economics: an estimate not unconnected with his reinterpretation of nineteenth-century economic thought as consisting of two streams or traditions commonly confused under the generic title of 'the classical tradition' against which Jevons so strongly reacted.