Two qualms about functionalist marxism

In Karl Marx's Theory of History: A Defence (1978), G. A. Cohen has developed a distinctively functionalist interpretation of historical materialism. In this paper I outline Cohen's novel reconstruction of Marx and subject it to two independent internal criticisms. I first argue that explanations cannot conform to Cohen's functionalist model. I then suggest that even if there could be explanations having the structure he has proposed, they would fail to be helpful in illuminating the causal kernel of Marx's theory. Finally I sketch a neglected but more promising approach to clarifying historical materialism, due to Geoffrey Hellman