This book began as an attempt by James Tully and myself to write a complete and up-to-date history of political thought in seventeenth century Europe. I agreed to cover the first half of the century, with Hobbes's mature work (and in particular of course Leviathan, published conveniently for our purposes in 1651) as the climax of my story; Tully's volume was to take the narrative down to the formation of the developed European state system at the Treaty of Utrecht. Once we had agreed the division of responsibility, we also agreed that we would work on the two volumes largely independently from one another, so that the books would not be in the usual sense a product of joint authorship. Since then, the two volumes have developed very separate lives, and they must be judged accordingly by the reader when they have both appeared.

But whatever their differences, there will also be a fundamental similarity between the approach in the two books. Tully and I have discussed our work together ever since we were graduate students in Cambridge, and despite our many differences of opinion and emphasis, we share two beliefs about how the history of political thought should be written. One of them is that to understand the political theories of any period we need to be historians, and we have each been very keen to depict as far as possible the character of the actual life which these theorists were leading, and the specific political questions which engaged their attention.