COMMUNICATION Joan Robinson and Marxism Today AFTER carefulh reading Professor Joan Robinson's article in Social Scientist (March 1973) I am inclined to offer the following comments. Theory of Value In Volume III of Capital in the chapter on the "Equalisation of the General Rate of Profit", Marx shows full awareness of the contradiction between his law of value and his law of the equalisation of the rate of profit per unit of capital. He says: It is prima facie two entirely different matters whether commodities are sold at their values (i. e. exchanged in proportion to the value contained in them at prices corresponding to their value) or whether they arc sold at such prices that their sale yields equal profits for equal masses of capitals advanced for their respective production... The whole difficulty arises from the fact that commodities are not exchanged simply as commodities but as products of capitals which claim participation in the total amount of surplus-value, proportional to their magnitude, or equal if they are of equal magnitude.1 Engels in his supplement to Volume III quotes Marx : The exchange of commodities at their values or approximately at their values, thus requires a much lower stage than their exchange at their prices of production, which requires a definite level of capitalist development ... Apart from the domination of prices and price movement by the law of value, it is quite appropriate to regard the values of commodities as not only theoretically but also historically prius to the prices of production. This applies to conditions in which the labourer owns his means of production. . . .2 In the same Supplement Engels stated, "We are dealing here not only with a purely logical process, but with a historical process and its explanatory reflection in thought, the logical pursuance of its inner connections9 ?.3 Then follows a discussion by Engels about how the equalisation of