If Alfred Marshall had been a baseball player, he be in the Hall of Fame. In fact, he was a great English economist who made his contribution to economics at the end of the nineteenth century. Before Marshall, economics was considered to be an esoteric discipline, intellectually accessible to only a small number of people. He had the view that economics ought to be accessible to ordinary intelligent people and he set out to demonstrate the essential ideas of what we call microeconomics using simple algebra and geometry. A century later, the introductory economics texts  used in colleges everywhere, are still indebted to his book Principles of Economics.