Review of Agriculture December 1978 that is where they fail. To say this, one need not go' into whether Weizsac- ker-Samuelson are right in saying that there is no exploitation under capitalism when capitalists invest all their, income. Moreover, to deny neo-clas- sicals by the assertion that where there is. exploitation there will be contradiction is to proceed in a rather didactic fashion, when what is needed is a clear counter-argument which results in this conclusion.