One good reply is that studying the history of economic thought can save individuals the time and expense of reinventing the wheel. E.g. The debates about contestability (i.e. the power of potential entry to discipline even firms which apparently had substantial monopoly power) from the 1980s are echoes of the arguments of John Bates Clark, Jeremiah Jenks (See my article on Jenks in the Journal of the History of Economic Thought (March 04) for a discussion of other parallels to later economic thought), and others in the 1890s and early 1900s. John Howard Brown