 Now it is apparent that this renders historical materialism consistent. Yet there is a question as to whether it is at too high a price. For we must ask whether functional explanation is a coherent methodological device. The problem is that we can ask what it is that makes it the case that an economic structure will only persist for as long as it develops the productive forces. Jon Elster has pressed this criticism against Cohen very hard (Elster 1985: 27–35). If we were to argue that there is an agent guiding history who has the purpose that the productive forces should be developed as much as possible then it would make sense that such an agent would intervene in history to carry out this purpose by selecting the economic structures which do the best job. However, it is clear that Marx makes no such metaphysical assumptions. Elster is very critical—sometimes of Marx, sometimes of Cohen—of the idea of appealing to “purposes” in history without those being the purposes of anyone.