William Stanley Jevons was an English economist and one of the three men who pioneered the Marginal Revolution. In fact, he was the first of the three to discover the subjective theory of value. His major works were A General Mathematical Theory of Political Economy, The Coal Question, Elementary Lessons on Logic, The Theory of Political Economy, and The State in Relation to Labor. In The Coal Question, he writes how (in his time) coal is probably the most important substance in their modern civilization. However, since the supply of coal is finite, it will get pricier and pricier to mine. He then presents the “Jevons Paradox”: if you increase the efficiency of coal-burning machines, the rate of consumption of coal will go up. People can now do the same amount of work with a smaller amount of fuel, thus making the use of that fuel more cost-effective.