History is difficult because people never state their assumptions or describe the framework in which their lives are led. To the extent that you do not unthinkingly supply these from your own experience, you can only guess at them from what your actors said and did. There will be no more evidence for the most important lines in your picture than that they fit with the demonstrable detail. They are either obvious or wrong. Maitland's indestructible memorial is that the great outlines he drew of the history of the common law, for which so much material survives, have so long seemed obvious. New or unnoticed detail at last begins to obtrude: but you cannot usefully erase an outline, only propose what seems a better fit.

This book will be about a small part of his picture, but one in which our understanding of the law is peculiarly entwined with our understanding of contemporary life. It will try to reconstruct what may be called the feudal component in the framework of English society in the years around 1200, the earliest time at which we know enough of what people said and did to make out what did not need saying and what it was not thinkable to do.

The things said and done are nearly all taken from Glanvill and from the plea rolls surviving from the reigns of Richard and John; and the lawyer trespassing in historians' country knows that he compounds his offence by concentrating on the legal sources.