David Harvey: The analysis of capitalism suggests that there are significant and foundational contradictions. Periodically those contradictions get out of hand and they generate a crisis. We’ve just been through a crisis and I think it’s important to ask, what were the contradictions that led us into it? How can we analyse the crisis in terms of contradictions? One of Marx’s great sayings was that a crisis is always the result of the underlying contradictions. Therefore we have to deal with those themselves rather than their results.