Some civil wars are easily predicted. They split the polity concerned along an obvious fault-line created by race, geography, religion, patronage ties, or economic dealings. They happen where the centre is relatively weak, where sectional attachments trump wider loyalties. But there are other, more unusual conflicts in which the usual pattern appears to be reversed, in which the tug exerted by the values of the centre (or some interpretation of those values) creates new groups that cut across existing social structures. The English civil war was one such conflict. The English fought each other in 1642 because their precociously unified national culture turned out to have ambiguous political implications. Both sides maintained, apparently sincerely, that they were fighting for the king, the laws, and the established Protestant religion, but each side turned out to be loyal to different understandings of these concepts. The cluster of apparently shared values was powerful enough to split the nation's governing class and to produce both royalists and roundheads in virtually all areas of the country. The kind of war the English fought reveals the kind of country that they lived in.
A satisfying history of early modern England must make this kind of war intelligible. No such account is likely to be wholly secular, for legalism, monarchy, and Protestant religion were intertwined and mutually supportive: the rights of church and crown were legal rights; the institutional structure of church and state was an expression of monarchical power; obedience to the King and to the law was a religious duty.