This paper argues that Marx's economics leads us to a deeper understanding of our current crisis than do either mainstream, Keynesian or 'mainstream Marxist' economics. First, Marx explains how a tendency for the rate of profit to fall in boom manifests in the generation and speculative investment of 'surplus' capital in the financial system/fictitious capital, providing a tendential basis for, rather than an accidental account of, financial bubbles/crises. Secondly, Marx's understanding that crisis is absolutely necessary to restore the profit rate, and so return the economy to boom, explains why developed countries' governments' attempts to postpone or limit crises since the 1970s have merely prevented a decisive enough crisis to restore the profit rate. Persistently low profitability has simply caused the world economy to stagnate, with persistently surplus capital taking many disruptive, adventurous paths. Finally, I consider how Marx's identification of when lending is 'lending', and when it is simply 'usury', can help us understand how the nature of the financial system has changed over the last forty years.
