What is the basis of all of the wealth in our modern global economy?For some it is merely the product of trade in a free market. The followers of Karl Marx, however, have enshrined the belief that all value, wealth and profit is generated by the working class and then stolen by the capitalist elites. The Marxist "Labour Theory of Value" lay at the heart of the communist revolutions that led to conflict and division throughout the twentieth century.Marx was 90 percent correct when he reasoned that one or more of the inputs into production must be paid far less than the value it generates in order to produce profit or "surplus value" at the end. Marx arrived at the bindingly obvious - and entirely wrong - conclusion that this input was labour.What Marx began to see toward the end of his life was that while labour could be exploited, automation meant that something else must be generating surplus value. In The Energy Theory of Value sociologist Tim Watkins argues that the "something else" that Marx missed was energy - in particular the one-time gift (and curse) of fossil carbon fuels.This understanding leads to a very different - and far more urgent - politics for the twenty-first century.