The subject of medieval economic thought is not in any sense a popular one – indeed, its mention is a positive conversation stopper. When I embarked upon it I had three basic assumptions. The first was that relatively little had been written about it. I could not have been more wrong. The bookshelves were already groaning, and the appearance of Odd Langholm's magisterial work, Economics in the Medieval Schools, in 1992 totally transformed the approach to the subject. The second assumption was that it would be possible to write about economic thought in isolation from economic practice. Those who were kind enough to read the first draft of my typescript soon pointed out this error. The result has been an attempt to integrate theory and practice, while desperately trying to keep the book to a manageable length. I am well aware that I have had to skate over many highly controversial areas of medieval economic history which deserve far deeper discussion than was possible here. The third assumption was that it should be feasible for someone like myself with no training in economics, but with experience in teaching medieval economic and social history (the two being inseparable) and the history of political ideas to write about medieval economic thought. I offer no judgement on this.